Work, Power And Machines Trivia Quiz!

1. Match the following:

Another name for the Newton-meter.

Must involve a force making an object move.

Transferred when work is done to an object.

The rate at which work is done.

This does not decrease the amount of work required.

Equal to 1 J/s.

Ratio of output work to input work.

Ratio of output force to input force.

This can be changed by a machine to affect output force if size and distance remain the same.

This affects the efficiency by converting some input work into thermal energy.

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2. According to scientists, which of the following are considered work?

Reading

Studying

Lifting weights

Moving a bookshelf

Lifting weights and moving a bookshelf are considered work because they involve exerting force to move an object against a resistance. Reading and studying, on the other hand, do not involve physical exertion or the application of force, so they are not considered work in the scientific sense.

Explanation

Lifting weights and moving a bookshelf are considered work because they involve exerting force to move an object against a resistance. Reading and studying, on the other hand, do not involve physical exertion or the application of force, so they are not considered work in the scientific sense.

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3. Work can occur without motion.

True

False

Motion must occur for work to be done.

Explanation

Motion must occur for work to be done.

4. A machine converts input work into output work.

True

False

The statement is true because a machine is designed to transform input work into output work. Machines use various mechanisms such as gears, levers, or pulleys to convert the energy supplied to them into useful work. This conversion can occur in different forms, such as mechanical, electrical, or thermal energy. Therefore, it is accurate to say that a machine converts input work into output work.

Explanation

The statement is true because a machine is designed to transform input work into output work. Machines use various mechanisms such as gears, levers, or pulleys to convert the energy supplied to them into useful work. This conversion can occur in different forms, such as mechanical, electrical, or thermal energy. Therefore, it is accurate to say that a machine converts input work into output work.

5. You push on an object for 5 seconds. During those 5 seconds, the object moves 0.87 m. After you stop pushing, the object moves another 0.30 m. The distance you should use to calculate work is ____________.

To find work, you only use the distance the object moved while force was applied.

Explanation

To find work, you only use the distance the object moved while force was applied.

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6. Work is done to lift an object off of the ground.

True

False

When an object is lifted off the ground, work is indeed done. Work is defined as the transfer of energy that occurs when a force is applied to an object, causing it to move in the direction of the force. In this case, the force applied is against the force of gravity, and as the object is lifted, energy is transferred to it. Therefore, work is being done to lift the object off the ground.

Explanation

When an object is lifted off the ground, work is indeed done. Work is defined as the transfer of energy that occurs when a force is applied to an object, causing it to move in the direction of the force. In this case, the force applied is against the force of gravity, and as the object is lifted, energy is transferred to it. Therefore, work is being done to lift the object off the ground.

7. Calculate the power used to move an object 3.0 m using 2 N of force over 2.5 seconds. (Hint: find work, then power) Work = Force x distance Power = Work/time

6 W

5 W

15 W

2.4 W

2 N x 3.0 m = 6 J
6 J/2.5 s = 2.4 W

Explanation

2 N x 3.0 m = 6 J
6 J/2.5 s = 2.4 W

8. Kinetic and potential energy increase when you lift something in the air.

True

False

When you lift something in the air, you are doing work against gravity. As a result, the object gains potential energy because it now has the ability to do work due to its elevated position. Additionally, as you lift the object, you are applying a force and causing it to move. This movement results in the object gaining kinetic energy, which is the energy of motion. Therefore, both the potential and kinetic energy of the object increase when it is lifted in the air.

Explanation

When you lift something in the air, you are doing work against gravity. As a result, the object gains potential energy because it now has the ability to do work due to its elevated position. Additionally, as you lift the object, you are applying a force and causing it to move. This movement results in the object gaining kinetic energy, which is the energy of motion. Therefore, both the potential and kinetic energy of the object increase when it is lifted in the air.

9. Only the part of a force that acts in the direction of motion does work.

True

False

This statement is true because work is defined as the product of the magnitude of the force and the displacement of the object in the direction of the force. If a force is acting perpendicular to the direction of motion, it will not contribute to the work done on the object. Only the component of the force that is parallel to the direction of motion will do work on the object. Therefore, only the part of a force that acts in the direction of motion does work.

Explanation

This statement is true because work is defined as the product of the magnitude of the force and the displacement of the object in the direction of the force. If a force is acting perpendicular to the direction of motion, it will not contribute to the work done on the object. Only the component of the force that is parallel to the direction of motion will do work on the object. Therefore, only the part of a force that acts in the direction of motion does work.

10. Moving something faster changes the amount of work done on the object in comparison to moving it in the same distance at a slower speed.

True

False

When an object is moved faster, it covers the same distance in less time. This means that the work done on the object is done in a shorter amount of time, resulting in a greater amount of work done per unit of time. Therefore, moving something faster does indeed change the amount of work done on the object in comparison to moving it at a slower speed.

Explanation

When an object is moved faster, it covers the same distance in less time. This means that the work done on the object is done in a shorter amount of time, resulting in a greater amount of work done per unit of time. Therefore, moving something faster does indeed change the amount of work done on the object in comparison to moving it at a slower speed.

11. A machine that has an output force that is equal to the input force has a mechanical advantage of less than one.

True

False

The formula for mechanical advantage is output force over input force. Any number over itself is one.

Explanation

The formula for mechanical advantage is output force over input force. Any number over itself is one.

12. One way a machine can make work easier is to change the direction of the force.

True

False

This statement is true because machines such as pulleys, levers, and inclined planes can change the direction of the force applied to them. By changing the direction of the force, these machines can make it easier to perform work by reducing the amount of force required. For example, a pulley can allow a person to lift a heavy object by pulling downwards instead of upwards, reducing the effort needed. Similarly, a lever can amplify a small input force to lift a much heavier load on the other end. Therefore, changing the direction of force is one way machines can make work easier.

Explanation

This statement is true because machines such as pulleys, levers, and inclined planes can change the direction of the force applied to them. By changing the direction of the force, these machines can make it easier to perform work by reducing the amount of force required. For example, a pulley can allow a person to lift a heavy object by pulling downwards instead of upwards, reducing the effort needed. Similarly, a lever can amplify a small input force to lift a much heavier load on the other end. Therefore, changing the direction of force is one way machines can make work easier.

13. The work done to lift an object off the ground is equal to the mass of the object multiplied by the distance it is lifted.

True

False

The work done to lift an object off the ground is equal to the weight of the object multiplied by the distance it is lifted.

Explanation

The work done to lift an object off the ground is equal to the weight of the object multiplied by the distance it is lifted.

14. Pamela uses a nutcracker to break an walnut. She applies a force of 24 N on the nutcracker. The force exerted on the almond is 60 N. Calculate the mechanical advantage of the nutcracker.MA = output force/input force

2.5

0.4

1,440

6

60 N/24 N = 2.5

Explanation

60 N/24 N = 2.5

15. The formula to calculate power is work times distance.

True

False

The formula to calculate power is work divided by time.

Explanation

The formula to calculate power is work divided by time.

16. You push on an object for 4 seconds with a force of 3 N. During those 4 seconds, the object moves 0.85 m. After you stop pushing, the object moves another 0.10 m. Calculate the work done on the object. Work = Force x distance

3.4 J

2.55 J

2.85 J

3.8 J

3 N x 0.85 m

Explanation

3 N x 0.85 m

17. Ross does 30 J of work with a lever. The output work of the elver is 25 J. Calculate the efficiency of the lever.Efficiency = output work/input work x 100

12%

8.3%

83%

120%

25 J/30 J x 100 = 83%

Explanation

25 J/30 J x 100 = 83%

18. A leaf rake makes work easier by increasing the output force.

True

False

A leaf rake makes work easier by increasing the output distance. A crowbar would make work easier by increasing the output force.

Explanation

A leaf rake makes work easier by increasing the output distance. A crowbar would make work easier by increasing the output force.

19. The efficiency of a machine is also a measure of

Friction

Accuracy

Work

Energy

Efficiency is a measure of how well a machine converts input energy into useful output energy. Friction is a force that opposes motion and causes energy loss in a machine. Therefore, the efficiency of a machine is affected by the presence of friction. Higher friction leads to lower efficiency as more energy is wasted in overcoming the resistance caused by friction. Hence, friction is a valid measure of a machine's efficiency.

Explanation

Efficiency is a measure of how well a machine converts input energy into useful output energy. Friction is a force that opposes motion and causes energy loss in a machine. Therefore, the efficiency of a machine is affected by the presence of friction. Higher friction leads to lower efficiency as more energy is wasted in overcoming the resistance caused by friction. Hence, friction is a valid measure of a machine's efficiency.

20. What does a machine do to the amount of work that needs to be done?

Decreases it

Increases it

Keeps it the same

Eliminates it

A machine keeps the amount of work that needs to be done the same. This means that the machine does not decrease or increase the workload, but rather helps to maintain it at a consistent level. Machines are designed to assist in performing tasks more efficiently and effectively, but they do not eliminate the need for work altogether.

Explanation

A machine keeps the amount of work that needs to be done the same. This means that the machine does not decrease or increase the workload, but rather helps to maintain it at a consistent level. Machines are designed to assist in performing tasks more efficiently and effectively, but they do not eliminate the need for work altogether.