Work Physics Quiz on Energy Transfer Concepts

1. The work done depends on the component of force in the direction of motion.

True

False

Concept: force component principle. Forces can be split into parallel and perpendicular components. The perpendicular component does no work on the displacement.

Explanation

Concept: force component principle. Forces can be split into parallel and perpendicular components. The perpendicular component does no work on the displacement.

2. When a force makes an angle (\theta) with displacement, the work done is:

(w = fdsin(theta))

(w = fdcos(theta))

(w = f/d)

(w = f+d)

Concept: work with an angle. Only the component of force along the displacement does work. That component is (fcos(theta)), so (w=(fcos(theta))d).

Explanation

Concept: work with an angle. Only the component of force along the displacement does work. That component is (fcos(theta)), so (w=(fcos(theta))d).

3. A student says 'work is the same as force.' The best correction is:

True, they are the same

Work depends on both force and displacement (and their direction)

Work is measured in newtons

Work is only about time

Concept: work requires displacement. Force alone does not guarantee work is done. Work measures energy transfer and needs displacement in the force direction.

Explanation

Concept: work requires displacement. Force alone does not guarantee work is done. Work measures energy transfer and needs displacement in the force direction.

4. Lifting an object of mass (m) by height (h) at constant speed requires work approximately equal to (mgh) (ignoring air resistance).

True

False

Concept: work against gravity. At constant speed, your upward force roughly balances weight (mg). Work is (w=fh ≈ mgh).

Explanation

Concept: work against gravity. At constant speed, your upward force roughly balances weight (mg). Work is (w=fh ≈ mgh).

5. If the net work on an object is negative, its kinetic energy:

Must increase

Decreases

Stays the same

Becomes infinite

Concept: sign of net work. Negative net work removes kinetic energy. This happens when resistive forces dominate.

Explanation

Concept: sign of net work. Negative net work removes kinetic energy. This happens when resistive forces dominate.

6. Pushing a box across a rough floor at constant speed means your work is mainly converted into:

Gravitational potential energy

Thermal energy (heat) due to friction

Nuclear energy

Light energy only

Concept: work against friction. Your work compensates for friction’s negative work. That energy is dissipated as heat in the surfaces.

Explanation

Concept: work against friction. Your work compensates for friction’s negative work. That energy is dissipated as heat in the surfaces.

7. A machine does 80 j of useful work using 100 j of input energy. Its efficiency is:

0.8%

8%

80%

180%

Concept: efficiency calculation. Efficiency (= 80/100 = 0.80). As a percent, that is 80%.

Explanation

Concept: efficiency calculation. Efficiency (= 80/100 = 0.80). As a percent, that is 80%.

8. The best overall summary is:

Work is always (fd) no matter what

Work is (fdcos(theta)); net work changes kinetic energy, and real systems lose energy to friction so efficiency is below 100%

Friction does positive work

Efficiency is output divided by time

Concept: grade 10 work recap. Angle matters because only the parallel component contributes. Work connects directly to energy changes, and real machines have losses that limit efficiency.

Explanation

Concept: grade 10 work recap. Angle matters because only the parallel component contributes. Work connects directly to energy changes, and real machines have losses that limit efficiency.

9. If you carry a suitcase horizontally at constant height, the work done by your upward force is approximately zero (ignoring small vertical motion).

True

False

Concept: perpendicular force. Your force is upward while displacement is horizontal. With (theta = 90⁰), the cosine term makes work zero.

Explanation

Concept: perpendicular force. Your force is upward while displacement is horizontal. With (theta = 90⁰), the cosine term makes work zero.

10. The work done by gravity when an object falls straight down a height (h) is:

(-mgh)

(+mgh)

0

(mgh/2)

Concept: sign of gravitational work. Gravity and displacement are in the same direction during a fall. That makes the work done by gravity positive.

Explanation

Concept: sign of gravitational work. Gravity and displacement are in the same direction during a fall. That makes the work done by gravity positive.

11. No real machine can be 100% efficient because some energy is always dissipated (e.g., friction).

True

False

Concept: real-world losses. Friction, air resistance, and internal deformation convert energy into heat and sound. That reduces the fraction available as useful output.

Explanation

Concept: real-world losses. Friction, air resistance, and internal deformation convert energy into heat and sound. That reduces the fraction available as useful output.

12. Friction does negative work because it acts opposite the direction of motion.

True

False

Concept: negative work from opposing force. The dot product fd is negative when force opposes displacement. That corresponds to energy being removed from motion.

Explanation

Concept: negative work from opposing force. The dot product fd is negative when force opposes displacement. That corresponds to energy being removed from motion.

13. If an object moves at constant speed in a straight line, the net work on it is zero.

True

False

Concept: constant speed implies no change in kinetic energy. If speed is constant, kinetic energy stays constant. By the work–energy theorem, net work must be zero.

Explanation

Concept: constant speed implies no change in kinetic energy. If speed is constant, kinetic energy stays constant. By the work–energy theorem, net work must be zero.

14. The work–energy theorem states that net work on an object equals the change in its kinetic energy.

True

False

Concept: work–energy theorem. Net work includes all forces’ contributions. Positive net work increases kinetic energy, and negative net work decreases it.

Explanation

Concept: work–energy theorem. Net work includes all forces’ contributions. Positive net work increases kinetic energy, and negative net work decreases it.

15. If you slowly lower a mass at constant speed, your work is negative (you apply an upward force while displacement is downward).

True

False

Concept: opposing displacement. Your force is opposite the displacement, so (w) is negative for your force. Gravity does positive work of equal magnitude if speed stays constant.

Explanation

Concept: opposing displacement. Your force is opposite the displacement, so (w) is negative for your force. Gravity does positive work of equal magnitude if speed stays constant.

16. A 50 N force pulls a box 4 m horizontally. If the force is at 60° above horizontal, the work done is:

200 j

100 j

50 j

Concept: using (w=fdcos(theta)). (w = 50 * 4 * cos60⁰). Since (cos60⁰ = 0.5), (w = 100) j.

Explanation

Concept: using (w=fdcos(theta)). (w = 50 * 4 * cos60⁰). Since (cos60⁰ = 0.5), (w = 100) j.

17. Efficiency is useful output energy (or work) divided by total input energy (or work), often expressed as a ______.

Concept: efficiency definition. Efficiency compares how much input becomes useful output. The rest is 'lost' to heat, sound, deformation, etc.

Explanation

Concept: efficiency definition. Efficiency compares how much input becomes useful output. The rest is 'lost' to heat, sound, deformation, etc.

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18. The dot-product idea for work can be written as w = fd = fdcos(theta), where (theta) is the angle between force and ______.

Concept: dot product meaning. Work depends on alignment of force and displacement. The cosine factor captures how much of the force points along the motion.

Explanation

Concept: dot product meaning. Work depends on alignment of force and displacement. The cosine factor captures how much of the force points along the motion.

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19. If (\theta = 90⁰), then (cos(theta) = ______) and the work done is zero.

Concept: perpendicular force gives zero work. A 90° angle means force is perpendicular to displacement. The parallel component is zero, so work is zero.

Explanation

Concept: perpendicular force gives zero work. A 90° angle means force is perpendicular to displacement. The parallel component is zero, so work is zero.

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20. If you lift a 2 kg object up by 3 m, the increase in gravitational potential energy is closest to:

6 j

20 j

60 j

600 j

Concept: gravitational potential energy. (Δ u = mgh ≈ 2 * 9.8 * 3 ≈ 58.8) j. Rounding gives about 60 j.

Explanation

Concept: gravitational potential energy. (Δ u = mgh ≈ 2 * 9.8 * 3 ≈ 58.8) j. Rounding gives about 60 j.

Work Physics Quiz: Test Your Understanding of Energy Transfer

1. The work done depends on the component of force in the direction of motion.

2.

What first name or nickname would you like us to use?

2. When a force makes an angle (\theta) with displacement, the work done is:

3. A student says 'work is the same as force.' The best correction is:

4. Lifting an object of mass (m) by height (h) at constant speed requires work approximately equal to (mgh) (ignoring air resistance).

5. If the net work on an object is negative, its kinetic energy:

6. Pushing a box across a rough floor at constant speed means your work is mainly converted into:

7. A machine does 80 j of useful work using 100 j of input energy. Its efficiency is:

8. The best overall summary is:

9. If you carry a suitcase horizontally at constant height, the work done by your upward force is approximately zero (ignoring small vertical motion).

10. The work done by gravity when an object falls straight down a height (h) is:

11. No real machine can be 100% efficient because some energy is always dissipated (e.g., friction).

12. Friction does negative work because it acts opposite the direction of motion.

13. If an object moves at constant speed in a straight line, the net work on it is zero.

14. The work–energy theorem states that net work on an object equals the change in its kinetic energy.

15. If you slowly lower a mass at constant speed, your work is negative (you apply an upward force while displacement is downward).

16. A 50 N force pulls a box 4 m horizontally. If the force is at 60° above horizontal, the work done is:

17. Efficiency is useful output energy (or work) divided by total input energy (or work), often expressed as a ______.

18. The dot-product idea for work can be written as w = fd = fdcos(theta), where (theta) is the angle between force and ______.

19. If (\theta = 90⁰), then (cos(theta) = ______) and the work done is zero.

20. If you lift a 2 kg object up by 3 m, the increase in gravitational potential energy is closest to: