MCAT Physics Practice Test 2: Work and Energy

Test Information

15 questions

minutes

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1. A weight lifter lifts a 275 kg barbell from the ground to a height of 2.4 m. How much work has he done in lifting the barbell, and how much work is required to hold the weight at that height?

• A. 3234 J and 0 J, respectively
• B. 3234 J and 3234 J, respectively
• C. 6468 J and 0 J, respectively
• D. 6468 J and 6468 J, respectively

2. A tractor pulls a log with a mass of 500 kg along the ground for 100 m. The rope (between the tractor and the log) makes an angle of 30° with the ground and is acted on by a tensile force of 5000 N. How much work does the tractor perform in this scenario? (Note: sin 30° = 0.5, cos 30° = 0.866, tan 30° = 0.577)

• A. 250 kJ
• B. 289 kJ
• C. 433 kJ
• D. 500 kJ

3. A 2000 kg experimental car can accelerate from 0 to in 6 s. What is the average power of the engine needed to achieve this acceleration?

• A. 150 W
• B. 150 kW
• C. 900 W
• D. 900 kW

4. A 40 kg block is resting at a height of 5 m off the ground. If the block is released and falls to the ground, which of the following is closest to its total mechanical energy at a height of 2 m, assuming negligible air resistance?

• A. 0 J
• B. 400 J
• C. 800 J
• D. 2000 J

5. 5 m3 of a gas are brought from an initial pressure of 1 kPa to a pressure of 3 kPa through an isochoric process. During this process, the work performed by the gas is:

• A. –10 kJ
• B. –10 J
• C. 0 J
• D. +10 kJ

6. In the pulley system shown below, which of the following is closest to the tension force in each rope if the mass of the object is 10 kg and the object is accelerating upwards at

• A. 50 N
• B. 60 N
• C. 100 N
• D. 120 N

7. Which of the following is a conservative force?

• A. Air resistance
• B. Friction
• C. Gravity
• D. Convection

8. During uniform circular motion, which of the following relationships is necessarily true?

• A. No work is done.
• B. The centripetal force does work.
• C. The velocity does work.
• D. Potential energy depends on position of the object around the circle.

9. Which of the following best characterizes the work–energy theorem?

• A. The work done by any force is proportional only to the magnitude of that force.
• B. The total work done on any object is equal to the change in kinetic energy for that object.
• C. The work done on an object by any force is proportional to the change in kinetic energy for that object.
• D. The work done by an applied force on an object is equal to the change in kinetic energy of that object.

10. A massless spring initially compressed by a displacement of two centimeters is now compressed by four centimeters. How has the potential energy of this system changed?

• A. The potential energy has not changed.
• B. The potential energy has doubled.
• C. The potential energy has increased by two joules.
• D. The potential energy has quadrupled.

11. Josh, who has a mass of 80 kg, and Sarah, who has a mass of 50 kg, jump off a 20 m tall building and land on a fire net. The net compresses, and they bounce back up at the same time. Which of the following statements is NOT true?

• A. Sarah will bounce higher than Josh.
• B. For Josh, the change in speed from the start of the jump to contacting the net is
• C. Josh will experience a greater force upon impact than Sarah.
• D. The energy in this event is converted from potential to kinetic to elastic to kinetic.

12. A parachutist jumps from a plane. Beginning at the point when she reaches terminal velocity, which of the following is/are true?

I. The jumper is in translational equilibrium.

II. The jumper is not being acted upon by any forces.

III. There is an equal amount of work being done by gravity and air resistance.

• A. I only
• B. I and III only
• C. II and III only
• D. I, II, and III

13. Mechanical advantage and efficiency are both ratios. Which of the following is true regarding the quantities used in these ratios?

• A. Mechanical advantage compares values of work; efficiency compares values of power.
• B. Mechanical advantage compares values of forces; efficiency compares values of work.
• C. Mechanical advantage compares values of power; efficiency compares values of energy.
• D. Mechanical advantage compares values of work; efficiency compares values of forces.

14. If the gravitational potential energy of an object has doubled in the absence of nonconservative forces, which of the following must be true, assuming the total mechanical energy of the object is constant?

• A. The object has been lifted to twice its initial height.
• B. The kinetic energy of the object has been halved.
• C. The kinetic energy has decreased by the same quantity as the potential energy has increased.
• D. The mass of the object has doubled.

15. A consumer is comparing two new cars. Car A exerts 250 horsepower, while Car B exerts 300 horsepower. The consumer is most concerned about the peak velocity that the car can reach. Which of the following statements would best inform the consumer's decision? (Note: 1 horsepower = 745.7 W)

• A. Car A and Car B both have unlimited velocities, ignoring nonconservative forces.
• B. Car A will reach its peak velocity more quickly than Car B.
• C. Car A will dissipate less energy to the surroundings than Car B.
• D. Car A will have a lower peak velocity than Car B.

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