AbrariAbrari
Practice
Menu
PapersTopicsTextbooksCOC / TVET

Physics · EUEE topic

Dynamics, work-energy and momentum: every EUEE question 2015–2017 E.C. (31 questions), solved

31 questions · 2015 ×8 · 2016 ×12 · 2017 ×11

Newton’s laws, work, energy, impulse and collisions from EUEE Physics 2015–2017 E.C.

Abrari is an independent study aid and is not affiliated with, endorsed by, or an official product of the Ethiopian Ministry of Education (MoE) or EAES.

Free on Abrari

Practice all 31 questions on this topic free

Sign up free to practice these timed, with explanations.

Practice freeSign up free

Read textbooks

Video coming soon

No explainer Short is attached to this topic yet. The slot stays empty until a YouTube id is stored in the topic data — we do not embed a broken player.

Abrari on Telegram

Read first

Open the textbook unit on site.

2015 E.C.

2015 E.C. · natural · Q15 · Moment of force

Two coplanar forces acts on a uniform beam as shown in the figure below. The moment of force on the beam is

This item uses a figure in the original paper (not redrawn here).

  1. A. 48.0 Nm.
  2. B. 12.0 Nm.
  3. C. 30.0 Nm.
  4. D. 24.0 Nm.
Worked solutionUnofficial

No keyed letter is published for this item. No keyed letter is published for this 2015 E.C. natural item (Moment of force). Moment depends on force magnitudes and lever arms shown in the figure.Try the options yourself, then practise the same subject timed in the app.

Practice this in the app

2015 E.C. · natural · Q21 · Newton's third law

Suppose you are standing on a horizontal floor, in a room, with one of your feet and leaning the wall of the room with the other foot. The number of action reaction pair of forces you experience is
  1. A. 1.
  2. B. 3.
  3. C. 2.
  4. D. 4.
Worked solutionUnofficial

Answer: B

Answer B: 3.. The stem is: Suppose you are standing on a horizontal floor, in a room, with one of your feet and leaning the wall of the room with the other foot. The number of action reaction pair of forces you experience is Letter B is the Abrari key for this Newton's third law.

📖 G11 Physics, Unit 4, §4.3, p. 111“Explore the relationship between Force, Mass, and Acceleration.”

Unofficial — solved by Abrari, not an official EAES key.

Practice this in the app

2015 E.C. · natural · Q24 · Impulse and momentum

A car of mass 1.50 × 10³ kg collides with a wall and rebounds. The initial and final velocities of the car are v1=−15.0v_1 = -15.0 m/s and v2=2.60v_2 = 2.60 m/s respectively. If the collision lasts for 0.15 s, what is the magnitude of the average force exerted on the car?
  1. A. 2.60 × 10⁴ N
  2. B. 3.96 × 10³ N
  3. C. 2.64 × 10⁴ N
  4. D. 1.76 × 10⁵ N
Worked solutionUnofficial

Answer: D

Answer D: 1.76 × 10⁵ N. The stem is: A car of mass 1.50 × 10³ kg collides with a wall and rebounds. The initial and final velocities of the car are v1=−15.0v_1 = -15.0 m/s and v2=2.60v_2 = 2.60 m/s respectively. If the collision lasts for 0.15 s, what is the magnitude of the average force exerted on the car? Letter D is the Abrari key for this Impulse and momentum.

📖 G11 Physics, Unit 4, §4.6, p. 154“4.6 Impulse and Linear Momentum By the end of this section, you will be able to: discuss impulse and linear momentum relate impulses to collisions”

Unofficial — solved by Abrari, not an official EAES key.

Practice this in the app

2015 E.C. · natural · Q25 · Work by friction

Starting from rest, a block of mass 5.0 kg slides 2.5 m down a rough 37° incline. The coefficient of kinetic friction between the block and the incline is µk=0.44µ_k = 0.44. What is the work done by the friction force on the block?
  1. A. -75.00 J
  2. B. -18.92 J
  3. C. -44.00 J
  4. D. -59.00 J
Worked solutionUnofficial

Answer: C

Answer C: -44.00 J. The stem is: Starting from rest, a block of mass 5.0 kg slides 2.5 m down a rough 37° incline. The coefficient of kinetic friction between the block and the incline is µk=0.44µ_k = 0.44. What is the work done by the friction force on the block? Letter C is the Abrari key for this Work by friction.

📖 G11 Physics, Unit 4, §4.4, p. 134“By the end of this section, you will be able to: define work in terms of the applied force and the displacement.”

Unofficial — solved by Abrari, not an official EAES key.

Practice this in the app

2015 E.C. · natural · Q35 · Potential energy in fields

Consider a point charge Q in an electrostatic field and a point mass m in a gravitational field. Which one of the following statements is correct about the potential energy of the objects?
  1. A. The electric potential decreases as a positive charge moves opposite to the electric field while the gravitational potential of the mass increases when it moves along the gravitational field.
  2. B. The potential energy of the point charge and that of the point mass changes as they move over equipotential surfaces in their respective fields.
  3. C. The potential energies at distance r, from the field sources for both Q and m vary inversely with r².
  4. D. The gravitational force on mass m is in the same direction of the gravitational field while the electric force on Q in the same or opposite directions depending the sign of the charge.
Worked solutionUnofficial

Answer: D

Answer D: The gravitational force on mass m is in the same direction of the gravitational field while the electric force on Q in the same or opposite directions depending the sign of the ch…. The stem is: Consider a point charge Q in an electrostatic field and a point mass m in a gravitational field. Which one of the following statements is correct about the potential energy of the objects? Letter D is the Abrari key for this Potential energy in fields.

📖 G11 Physics, Unit 4, §4.4, p. 134“By the end of this section, you will be able to: define work in terms of the applied force and the displacement.”

Unofficial — solved by Abrari, not an official EAES key.

Practice this in the app

2015 E.C. · natural · Q47 · Friction on incline

A man pushes a 25.0 kg object by 250 N force along an inclined plane inclined at an angle of 37° to the horizontal. If the object moves with constant speed, the friction force exerts on the block is
  1. A. 250.0 N, up the inclined plane.
  2. B. 100.0 N, up the inclined plane.
  3. C. 100.0 N, down the inclined plane.
  4. D. 250.0 N, down the inclined plane.
Worked solutionUnofficial

Answer: C

Answer C: 100.0 N, down the inclined plane.. The stem is: A man pushes a 25.0 kg object by 250 N force along an inclined plane inclined at an angle of 37° to the horizontal. If the object moves with constant speed, the friction force exerts on the block is Letter C is the Abrari key for this Friction on incline.

Unofficial — solved by Abrari, not an official EAES key.

Practice this in the app

2015 E.C. · natural · Q48 · Collisions

The following three collisions occur in different systems. I. A billiard ball A collides with an identical ball B and comes to rest after collision, while ball B moves with the same velocity as ball A was moving before. II. A bullet moving with speed v hits a suspended mass and is embedded in it and the combination moves with common velocity. III. Two cars moving in opposite direction become at rest after collision. Which of the following statements is correct about these collisions?
  1. A. If and III are inelastic collisions.
  2. B. I and II are elastic collisions.
  3. C. I, II and III are inelastic collisions.
  4. D. I and III are elastic collisions.
Worked solutionUnofficial

No keyed letter is published for this item. No keyed letter is published for this 2015 E.C. natural item (Collisions). Physically I is elastic while II and III are inelastic; no option matches exactly. Source options may be garbled (e.g. 'If and III' in A). Verify intended answer key.Try the options yourself, then practise the same subject timed in the app.

Practice this in the app

2015 E.C. · natural · Q49 · Energy in SHM (spring)

An object of mass M is attached to a spring of spring constant K, as shown in the figure below. If the mass is pulled to a point P, which is at distance A from equilibrium position O, and released, Which one of the following statements is correct about energy of the system? (assume the surface is frictionless)

This item uses a figure in the original paper (not redrawn here).

  1. A. At point O, the system has both kinetic and potential energy.
  2. B. At point P, the system has both kinetic energy and potential energy.
  3. C. At point P, the mass attain its maximum velocity.
  4. D. At point Q the system has both kinetic energy and potential energy.
Worked solutionUnofficial

Answer: D

Answer D: At point Q the system has both kinetic energy and potential energy.. The stem is: An object of mass M is attached to a spring of spring constant K, as shown in the figure below. If the mass is pulled to a point P, which is at distance A from equilibrium position O, and released, Which one of the following statements is correct about energy of the system? (ass… Letter D is the Abrari key for this Energy in SHM (spring). Answer assumes Q is an intermediate point between O and P (per figure); at an intermediate point the system has both KE and PE.

Unofficial — solved by Abrari, not an official EAES key.

Practice this in the app

2016 E.C.

2016 E.C. · natural · Q1 · Units / torque

In the following choices, given that the symbols N, m, J, kg, stand for Newton, meter, Joule, and kilogram, respectively, then which one is the correct SI unit of torque?
  1. A. N
  2. B. kg m²
  3. C. N m = J
  4. D. N m ≠ J
Worked solutionUnofficial

Answer: C

Answer C: N m = J. The stem is: In the following choices, given that the symbols N, m, J, kg, stand for Newton, meter, Joule, and kilogram, respectively, then which one is the correct SI unit of torque? Letter C is the Abrari key for this Units / torque. Torque unit is N·m, dimensionally equal to J.

📖 G11 Physics, Unit 4, §4.3, p. 111“Explore the relationship between Force, Mass, and Acceleration.”

Unofficial — solved by Abrari, not an official EAES key.

Practice this in the app

2016 E.C. · natural · Q6 · Rotational dynamics / work

An electric motor exerts a constant 10 N⋅m torque on a grindstone, which has a moment of inertia of 5.0 kg⋅m2 about its axis. The system starts from rest and turns. What is the work done by the motor in 4.0 s?
  1. A. 160 J
  2. B. 40 J
  3. C. 2 J
  4. D. 320 J
Worked solutionUnofficial

Answer: A

Answer A: 160 J. The stem is: An electric motor exerts a constant 10 N⋅m torque on a grindstone, which has a moment of inertia of 5.0 kg⋅m2 about its axis. The system starts from rest and turns. What is the work done by the motor in 4.0 s? Letter A is the Abrari key for this Rotational dynamics / work. α=τ/I=2 rad/s²; θ=½αt²=16 rad; W=τθ=160 J.

📖 G11 Physics, Unit 4, §4.4, p. 134“By the end of this section, you will be able to: define work in terms of the applied force and the displacement.”

Unofficial — solved by Abrari, not an official EAES key.

Practice this in the app

Free on Abrari

Keep practicing this topic free

Create a free account to practice this topic with saved progress.

Practice freeSign up free

2016 E.C. · natural · Q7 · Electrostatics / Coulomb force

Three charges Q1 = 5 x 10-10 C, Q2 = 2 x 10-10 C and Q3 = 3 x 10-10 C, are placed on the x axis at points x = 0, x = 2 cm and x = 4 cm, respectively, as shown in the figure below. What is the magnitude of electrostatic force exerted on Q2 by the other two charges?

This item uses a figure in the original paper (not redrawn here).

  1. A. 3.6 x 10-6 N
  2. B. 9 x 10-7 N
  3. C. 9 N
  4. D. 9 x 10-15 N
Worked solutionUnofficial

Answer: B

Answer B: 9 x 10-7 N. The stem is: Three charges Q1 = 5 x 10-10 C, Q2 = 2 x 10-10 C and Q3 = 3 x 10-10 C, are placed on the x axis at points x = 0, x = 2 cm and x = 4 cm, respectively, as shown in the figure below. What is the magnitude of electrostatic force exerted on Q2 by the other two charges? Letter B is the Abrari key for this Electrostatics / Coulomb force. F1=2.25e-6 N (right), F3=1.35e-6 N (left); net=9e-7 N. Figure only illustrates layout.

Unofficial — solved by Abrari, not an official EAES key.

Practice this in the app

2016 E.C. · natural · Q15 · Fluid dynamics / laminar flow

Which one of the following correctly describes the relationship between the factors affecting laminar flow?
  1. A. A fast moving object in air makes air to expand more.
  2. B. A fast moving object in air causes the air to become denser.
  3. C. The effect of temperature would be significant at low speeds.
  4. D. Viscosity has no effect in case when a fast moving object is taken.
Worked solutionUnofficial

Answer: A

Answer A: A fast moving object in air makes air to expand more.. The stem is: Which one of the following correctly describes the relationship between the factors affecting laminar flow? Letter A is the Abrari key for this Fluid dynamics / laminar flow. Ambiguous options; A chosen as least incorrect. Verify against official key.

Unofficial — solved by Abrari, not an official EAES key.

Practice this in the app

2016 E.C. · natural · Q16 · Newton's laws / equilibrium

A body is observed to be moving with constant velocity in a straight line. One can surely conclude that for this body,
  1. A. no external force is applied on it.
  2. B. no friction force is acting on it.
  3. C. constant force is applied on it.
  4. D. the net external force acting on it is zero.
Worked solutionUnofficial

Answer: D

Answer D: the net external force acting on it is zero.. The stem is: A body is observed to be moving with constant velocity in a straight line. One can surely conclude that for this body, Letter D is the Abrari key for this Newton's laws / equilibrium.

📖 G11 Physics, Unit 4, §4.3, p. 111“Explore the relationship between Force, Mass, and Acceleration.”

Unofficial — solved by Abrari, not an official EAES key.

Practice this in the app

2016 E.C. · natural · Q18 · Angular momentum / impulse

A constant torque of 80 Nm is applied to the rim of a flywheel for 2 s. If the flywheel initially has angular momentum of 40 kgm2/s, what will be its final angular momentum?
  1. A. 200 kgm2/s
  2. B. 40 kgm2/s
  3. C. 160 kgm2/s
  4. D. 120 kgm2/
Worked solutionUnofficial

Answer: A

Answer A: 200 kgm2/s. The stem is: A constant torque of 80 Nm is applied to the rim of a flywheel for 2 s. If the flywheel initially has angular momentum of 40 kgm2/s, what will be its final angular momentum? Letter A is the Abrari key for this Angular momentum / impulse. L_f = L_i + τt = 40 + 80×2 = 200.

📖 G11 Physics, Unit 4, §4.6, p. 154“4.6 Impulse and Linear Momentum By the end of this section, you will be able to: discuss impulse and linear momentum relate impulses to collisions”

Unofficial — solved by Abrari, not an official EAES key.

Practice this in the app

2016 E.C. · natural · Q23 · Renewable energy

Which one of the following types of renewable energy resources are characterized by no emission of greenhouse gases?
  1. A. Hydroelectric and Wind energy
  2. B. Wind and Geothermal energy
  3. C. Solar and Wind energy
  4. D. Geothermal and Solar energy
Worked solutionUnofficial

Answer: C

Answer C: Solar and Wind energy. The stem is: Which one of the following types of renewable energy resources are characterized by no emission of greenhouse gases? Letter C is the Abrari key for this Renewable energy. Solar and wind are zero-emission; geothermal/hydro can emit some gases.

Unofficial — solved by Abrari, not an official EAES key.

Practice this in the app

2016 E.C. · natural · Q24 · Dynamics / equilibrium

Which one of the following bodies is in linear equilibrium?
  1. A. A body moving with constantly changing velocity in straight line
  2. B. A body moving with constant velocity
  3. C. A body in uniformly accelerated motion in a straight line
  4. D. A body acted upon by a single constant force
Worked solutionUnofficial

Answer: B

Answer B: A body moving with constant velocity. The stem is: Which one of the following bodies is in linear equilibrium? Letter B is the Abrari key for this Dynamics / equilibrium.

Unofficial — solved by Abrari, not an official EAES key.

Practice this in the app

2016 E.C. · natural · Q27 · Dynamics / apparent weight

A student of mass 40 kg is in a lift moving upward with an acceleration of 2.5 m/s2. What is the apparent weight of the student?
  1. A. 500 N
  2. B. 800 N
  3. C. 400 N
  4. D. 300 N
Worked solutionUnofficial

Answer: A

Answer A: 500 N. The stem is: A student of mass 40 kg is in a lift moving upward with an acceleration of 2.5 m/s2. What is the apparent weight of the student? Letter A is the Abrari key for this Dynamics / apparent weight. W=m(g+a)=40(10+2.5)=500 N.

📖 G11 Physics, Unit 4, §4.3, p. 111“Explore the relationship between Force, Mass, and Acceleration.”

Unofficial — solved by Abrari, not an official EAES key.

Practice this in the app

2016 E.C. · natural · Q39 · Quantum / uncertainty principle

A light radiation is used to measure the position of an electron of wavelength 3 x 10-11 m. If the uncertainty in the momentum (ΔP) is 2.21 x 10-23 kgm/s, then according to the uncertainty principle, which one of the following is an acceptable value of the uncertainty in the position (Δx) of the electron?
  1. A. Δx = 3.0 x 10-13 m
  2. B. Δx = 1.5 x 10-15 m
  3. C. Δx = 3.0 x 10-11 m
  4. D. Δx = 1.5 x 10-14 m
Worked solutionUnofficial

Answer: C

Answer C: Δx = 3.0 x 10-11 m. The stem is: A light radiation is used to measure the position of an electron of wavelength 3 x 10-11 m. If the uncertainty in the momentum (ΔP) is 2.21 x 10-23 kgm/s, then according to the uncertainty principle, which one of the following is an acceptable value of the uncertainty in the pos… Letter C is the Abrari key for this Quantum / uncertainty principle. Δx ≥ ħ/(2Δp) ≈ 2.4e-12 m; only 3.0e-11 m satisfies this.

📖 G11 Chemistry, Unit 1, §1.4, p. 36“The electron in an hydrogen atom travels around the nucleus in a circular orbit.”

Unofficial — solved by Abrari, not an official EAES key.

Practice this in the app

2016 E.C. · natural · Q41 · Fundamental forces

One of the four fundamental forces of nature acting over long distances and purely attractive is
  1. A. electromagnetic force
  2. B. strong nuclear force
  3. C. weak nuclear force
  4. D. gravitational force
Worked solutionUnofficial

Answer: D

Answer D: gravitational force. The stem is: One of the four fundamental forces of nature acting over long distances and purely attractive is Letter D is the Abrari key for this Fundamental forces.

Unofficial — solved by Abrari, not an official EAES key.

Practice this in the app

2016 E.C. · natural · Q50 · Work-energy theorem

If a ball is thrown vertically upward with an initial velocity of v0 and reaches a maximum height h after time t, then during the time interval
  1. A. work done by gravity is greater than the initial kinetic energy
  2. B. work done by gravity is positive since kinetic energy increases
  3. C. work done by gravity equals the kinetic energy at h
  4. D. work done by gravity equals the change in the kinetic energy of the ball
Worked solutionUnofficial

Answer: D

Answer D: work done by gravity equals the change in the kinetic energy of the ball. The stem is: If a ball is thrown vertically upward with an initial velocity of v0 and reaches a maximum height h after time t, then during the time interval Letter D is the Abrari key for this Work-energy theorem. Work-energy theorem: W_gravity = ΔKE.

📖 G11 Physics, Unit 4, §4.4, p. 134“By the end of this section, you will be able to: define work in terms of the applied force and the displacement.”

Unofficial — solved by Abrari, not an official EAES key.

Practice this in the app

Free on Abrari

Keep practicing this topic free

Create a free account to practice this topic with saved progress.

Practice freeSign up free

2017 E.C.

2017 E.C. · natural · Q5 · momentum / collisions

Block A of mass m1_1 = 8.0 kg travelling initially at u1_1 = 6 m/s in the positive x-direction collides with block B of mass m2_2 = 12 kg moving in the same direction at u2_2 = 3 m/s. If the velocity of block A, immediately after the collision, is v1_1 = 4 m/s to the positive x-axis, what is the velocity of block B, immediately after the collision?
  1. A. 4.33 m/s to the negative x-axis
  2. B. 3.71 m/s to the negative x-axis
  3. C. 3.71 m/s to the positive x-axis
  4. D. 4.33 m/s to the positive x-axis
Worked solutionUnofficial

Answer: D

Answer D: 4.33 m/s to the positive x-axis. The stem is: Block A of mass m1_1 = 8.0 kg travelling initially at u1_1 = 6 m/s in the positive x-direction collides with block B of mass m2_2 = 12 kg moving in the same direction at u2_2 = 3 m/s. If the velocity of block A, immediately after the collision, is v1_1 = 4 m/s to the positi… Letter D is the Abrari key for this momentum / collisions. Momentum: 8*6 + 12*3 = 48+36 = 84. After: 8*4 + 12*v2 = 32 + 12*v2 = 84 => v2 = 52/12 = 4.33 m/s positive x.

📖 G11 Physics, Unit 4, §4.6, p. 154“4.6 Impulse and Linear Momentum By the end of this section, you will be able to: discuss impulse and linear momentum relate impulses to collisions”

Unofficial — solved by Abrari, not an official EAES key.

Practice this in the app

2017 E.C. · natural · Q11 · inclined plane / mechanical advantage

A force is used to push a box of mass, m along the slope of an inclined plane with constant velocity. If the coefficient of friction between the box and the inclined plane be μ, the actual mechanical advantage (AMA) of the inclined plane is

This item uses a figure in the original paper (not redrawn here).

  1. A. 1/(cos⁡θ+μsin⁡θ)1/(\cos \theta + \mu \sin \theta)
  2. B. 1/(sin⁡θ+μcos⁡θ)1/(\sin \theta + \mu \cos \theta)
  3. C. (cos⁡θ+μsin⁡θ)(\cos \theta + \mu \sin \theta)
  4. D. (sin⁡θ+μcos⁡θ)(\sin \theta + \mu \cos \theta)
Worked solutionUnofficial

Answer: B

Answer B: 1/(sin⁡θ+μcos⁡θ)1/(\sin \theta + \mu \cos \theta). The stem is: A force is used to push a box of mass, m along the slope of an inclined plane with constant velocity. If the coefficient of friction between the box and the inclined plane be μ, the actual mechanical advantage (AMA) of the inclined plane is Letter B is the Abrari key for this inclined plane / mechanical advantage. Effort to push up = mg(sinθ + μcosθ), load lifted = mg. AMA = load/effort = 1/(sinθ + μcosθ).

Unofficial — solved by Abrari, not an official EAES key.

Practice this in the app

2017 E.C. · natural · Q14 · Newton's first law

According to Newton's first law, an object that is in motion continues its state of motion with
  1. A. constant velocity if the resultant force exerted on it is not zero.
  2. B. a decreasing speed if the resultant force exerted on it is zero.
  3. C. constant velocity if the resultant force exerted on it is zero.
  4. D. an increasing speed if the resultant force exerted on it is not zero.
Worked solutionUnofficial

Answer: C

Answer C: constant velocity if the resultant force exerted on it is zero.. The stem is: According to Newton's first law, an object that is in motion continues its state of motion with Letter C is the Abrari key for this Newton's first law.

📖 G11 Physics, Unit 4, §4.3, p. 111“Explore the relationship between Force, Mass, and Acceleration.”

Unofficial — solved by Abrari, not an official EAES key.

Practice this in the app

2017 E.C. · natural · Q20 · friction

When an object tends to slide over the surface of another object, tiny bumps at the surface of the two objects knocking and locking together. This causes
  1. A. frictional force.
  2. B. normal force.
  3. C. electrostatic force.
  4. D. gravitational force.
Worked solutionUnofficial

Answer: A

Answer A: frictional force.. The stem is: When an object tends to slide over the surface of another object, tiny bumps at the surface of the two objects knocking and locking together. This causes Letter A is the Abrari key for this friction.

Unofficial — solved by Abrari, not an official EAES key.

Practice this in the app

2017 E.C. · natural · Q21 · work and energy

Suppose a ball is thrown vertically upward and after reaching a maximum height, it returns back to its initial position. Which of the following statement is correct about energy changes and work done on the ball?
  1. A. On its way down, change in its potential energy is positive.
  2. B. On its way down, work done by gravity is positive.
  3. C. On its way up, change in its kinetic energy is positive.
  4. D. On its way up, work done by gravity is positive.
Worked solutionUnofficial

Answer: B

Answer B: On its way down, work done by gravity is positive.. The stem is: Suppose a ball is thrown vertically upward and after reaching a maximum height, it returns back to its initial position. Which of the following statement is correct about energy changes and work done on the ball? Letter B is the Abrari key for this work and energy. On way down, gravity acts in the direction of motion => work done by gravity is positive.

📖 G11 Physics, Unit 4, §4.4, p. 134“By the end of this section, you will be able to: define work in terms of the applied force and the displacement.”

Unofficial — solved by Abrari, not an official EAES key.

Practice this in the app

2017 E.C. · natural · Q22 · mechanical energy

The mechanical energy of an oscillating object at any point through its path is equal to
  1. A. the difference between its kinetic and potential energies.
  2. B. the sum of its potential and internal energies.
  3. C. the sum of its kinetic and internal energies.
  4. D. the sum of its kinetic and potential energies.
Worked solutionUnofficial

Answer: D

Answer D: the sum of its kinetic and potential energies.. The stem is: The mechanical energy of an oscillating object at any point through its path is equal to Letter D is the Abrari key for this mechanical energy.

Unofficial — solved by Abrari, not an official EAES key.

Practice this in the app

2017 E.C. · natural · Q23 · impulse / momentum

A tennis ball of mass 0.10 kg traveling horizontally at 40.0 m/s is struck back by a racket. If the ball returns back with a speed of 30.0 m/s in the opposite direction, what is the magnitude of the impulse delivered to the ball by the racket?
  1. A. 1.0 kg m/s
  2. B. 7.0 kg m/s
  3. C. 4.0 kg m/s
  4. D. 3.0 kg m/s
Worked solutionUnofficial

Answer: B

Answer B: 7.0 kg m/s. The stem is: A tennis ball of mass 0.10 kg traveling horizontally at 40.0 m/s is struck back by a racket. If the ball returns back with a speed of 30.0 m/s in the opposite direction, what is the magnitude of the impulse delivered to the ball by the racket? Letter B is the Abrari key for this impulse / momentum. Impulse = Δp = m(v_f - v_i) = 0.10*(-30 - 40) = -7.0 kg m/s, magnitude 7.0 kg m/s.

📖 G11 Physics, Unit 4, §4.6, p. 154“4.6 Impulse and Linear Momentum By the end of this section, you will be able to: discuss impulse and linear momentum relate impulses to collisions”

Unofficial — solved by Abrari, not an official EAES key.

Practice this in the app

2017 E.C. · natural · Q51 · fundamental forces

Which one of the following statements is correct about the fundamental forces in nature and their applications?
  1. A. The force that keeps the nucleus of an atom from flying apart due to the repulsive force between protons is the weak nuclear force.
  2. B. The gravitational force makes planets revolve around the Sun and follow their orbital path.
  3. C. The force that arises in most radioactive processes and in nuclear reactions that generate the Sun's energy is the strong nuclear force.
  4. D. The electromagnetic force is the force that keeps protons and neutrons bound together in the nucleus of an atom.
Worked solutionUnofficial

Answer: B

Answer B: The gravitational force makes planets revolve around the Sun and follow their orbital path.. The stem is: Which one of the following statements is correct about the fundamental forces in nature and their applications? Letter B is the Abrari key for this fundamental forces.

Unofficial — solved by Abrari, not an official EAES key.

Practice this in the app

2017 E.C. · natural · Q52 · elastic potential energy

A spring stores 120 J of elastic potential energy when it is stretched by 0.5 m. What is the potential energy stored by the spring when it is stretched by 1.5 m?
  1. A. 480 J
  2. B. 960 J
  3. C. 1080 J
  4. D. 540 J
Worked solutionUnofficial

Answer: C

Answer C: 1080 J. The stem is: A spring stores 120 J of elastic potential energy when it is stretched by 0.5 m. What is the potential energy stored by the spring when it is stretched by 1.5 m? Letter C is the Abrari key for this elastic potential energy. PE ∝ x². Stretch tripled (0.5→1.5), so PE × 9 = 120*9 = 1080 J.

📖 G11 Physics, Unit 4, §4.4, p. 134“By the end of this section, you will be able to: define work in terms of the applied force and the displacement.”

Unofficial — solved by Abrari, not an official EAES key.

Practice this in the app

2017 E.C. · natural · Q53 · power / work

A crane at port is used to lift a 10,000 kg object to a height of 20 m. If the power developed by the crane is 50,000 W, how long does it take to lift the object?
  1. A. 400 s
  2. B. 40 s
  3. C. 4 s
  4. D. 2 s
Worked solutionUnofficial

Answer: B

Answer B: 40 s. The stem is: A crane at port is used to lift a 10,000 kg object to a height of 20 m. If the power developed by the crane is 50,000 W, how long does it take to lift the object? Letter B is the Abrari key for this power / work. W = mgh = 10000*10*20 = 2e6 J. t = W/P = 2e6/5e4 = 40 s (using g=10). With g=9.8, ~39.2 s ≈ 40 s.

📖 G11 Physics, Unit 4, §4.4, p. 134“By the end of this section, you will be able to: define work in terms of the applied force and the displacement.”

Unofficial — solved by Abrari, not an official EAES key.

Practice this in the app

Free on Abrari

Practice all 31 questions on this topic free

Sign up free to practice these timed, with explanations.

Practice freeSign up free

Frequently asked questions

Are these Physics answers official?
No. Every keyed letter on this page is unofficial — solved by Abrari from the past paper, then checked against the textbook when a stored quote exists. Abrari never calls an answer an official EAES or MoE key.
Is Abrari affiliated with the Ministry of Education or EAES?
Abrari is an independent study aid and is not affiliated with, endorsed by, or an official product of the Ethiopian Ministry of Education (MoE) or EAES.
Can I download the textbook PDF?
No. Abrari does not offer textbook downloads. Mapped units open in the on-site reader only.
How do I practice these questions timed?
Use the practice links on this page or go to https://abrari.app/#try. The web try-out and the Abrari app use the same unofficial question bank.