CHAPTER 4 SECTIONS 1 & 2

Work, Power and

Machines

1. What is work?

• A. The type of energy that a moving object has

• B. The rate at which work is done or energy is transformed

• C. The unit used to express power• D. The transfer of energy using a force that causes an object to move in the direction of the force

ANSWER:

•Work is…•D. The transfer of energy using a force that causes an object to move in the direction of the force

2. What is power?

• A. The type of energy that a moving object has

• B. The rate at which work is done or energy is transformed

• C. The unit used to express power• D. The transfer of energy using a force that causes an object to move in the direction of the force

ANSWER

•Power is…•B. The rate at which work is done or energy is transformed

3. What is kinetic energy?

• A. The type of energy that a moving object

has• B. The rate at which work is done or energy is transformed

• C. The unit used to express power• D. The transfer of energy using a force that causes an object to move in the direction of the force

ANSWER

•Kinetic energy is …•A. The type of energy that a moving object has

4. What is a machine?

• A. The type of energy that a moving object

has• B. The rate at which work is done or energy is

transformed• C. A device that helps do work by either overcoming a force or changing the direction of the force

• D. The transfer of energy using a force that causes an object to move in the direction of the force

ANSWER

•A machine is…•C. A device that helps do work by either overcoming a force or changing the direction of the force

5. What is work input?

•A. A number that tells how many times a machine multiplies a force

•B. A quantity, usually expressed as a percentage, that measures the ratio of work output to work input

•C. The work done ON a machine•D. The work done BY a machine

ANSWER

•Work input is…•C. The work done ON a machine

6. What is work output?

•A. A number that tells how many times a machine multiplies a force

•B. A quantity, usually expressed as a percentage, that measures the ratio of work output to work input

•C. The work done ON a machine•D. The work done BY a machine

ANSWER

•Work output is…• D. The work done BY a machine

7. What is mechanical advantage?

•A. A number that tells how many times a machine multiplies a force

•B. A quantity, usually expressed as a percentage, that measures the ratio of work output to work input

•C. The work done ON a machine•D. The work done BY a machine

ANSWER

Mechanical advantage is…•A. A number that tells how many times a machine multiplies a force

8. What is mechanical efficiency?

•A. A number that tells how many times a machine multiplies a force

•B. A quantity, usually expressed as a percentage, that measures the ratio of work output to work input

•C. The work done ON a machine•D. The work done BY a machine

ANSWER

Mechanical efficiency is…•B. A quantity, usually expressed as a percentage, that measures the ratio of work output to work input

9. In which situation is a person doing work on an object?

• A. A school crossing guard raises a stop

sign that weighs 10 N.• B. A student walks while wearing a

backpack that weighs 15 N.• C. A man exerts 350 N force on a rope

attached to a house.• D. A worker holds a box 1 m off the floor.

ANSWER

•A. A school crossing guard raises a stop sign that weighs 10 N.

10. Scott applies a force of 100 N to move a box 5 meters. How much work did he do?

•A. 100 J•B. 500 J•C. 5 J•D. 500 N

ANSWER

•B. 500 J

11. If a barbell weighs 160 N, what other information do you need to calculate how much work it takes to lift it?

• A. The shape of the weights• B. The height the barbell is being lifted• C. The strength of the person doing the

lifting• D. The amount of output force

ANSWER

•B. The height the barbell is being lifted

12. Tom used 75 N of force to push a box 3 m across the floor. How much work did he do?

a. 25 J

b. 25 N

c. 225 J

d. 225 W

ANSWER

75 N x 3 m =

c. 225 J

13. Which of the following prevents machines from being 100% efficient?

a. friction

b. input force

c. output force

d. power

ANSWER

a. friction

GOOD LUCK ON TUESDAY!!

STUDY HARD!!

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