Work and Machines

Work equals Force times

A. B. C. D.

0% 0%

100%

0%

A. EnergyB. VelocityC. DistanceD. Mass

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

21 22 23 24 25 26 27 28 29 30 31 32

Work is measured in

A. B. C. D.

0% 0%

100%

0%

A. MetersB. PoundsC. JoulesD. Newtons

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

21 22 23 24 25 26 27 28 29 30 31 32

Work and Machines

1. Describe what a machine is and how it makes work easier to do.

2. Relate the work input to a machine to the work output of the machine.

Which of these is an example of work being done on an object?

A. B. C. D.

0%5%

86%

9%

A. Holding a heavy piece of wood at a construction site.

B. Trying to push a car that doesn’t move out of deep snow.

C. Pushing a child on a swing.D. Holding a door shut on a

windy day so it doesn’t blow open.

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

21 22 23 24 25 26 27 28 29 30 31 32

Machines Do Work A Machine is a device that

changes force. Machines make work easier to do

in three ways.1. Change the size of a force needed.2. Direction of a force3. Distance over which a force acts.

What do machines do?

A. B. C. D.

55%

0%

30%

15%

A. Change the amount of force you exert or the distance over which you exert the force.

B. Increase the amount of work that is done.

C. Decrease the amount of work that is done.

D. Eliminate friction.

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

21 22 23 24 25 26 27 28 29 30 31 32

Increasing Force The upward force exerted by the jack is greater

than the downward force you exert of the handle.

Increasing Distance They will do the same amount of work.

Doing the work over a longer distance allows them to use less force.

Changing Direction When you use an

ax to split wood, you exert a downward force as you swing the ax then it changes into a horizontal force that splits the wood apart.

How can a hockey stick be considered a machine?

A. B. C. D.

45%

0%

36%

18%

A. It multiplies force.B. It multiplies

distance.C. It changes

direction.D. It reduces friction.

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

21 22 23 24 25 26 27 28 29 30 31 32

Pulling down on a rope to hoist a sail on a sailboat is an example of a machine.

A. B. C. D.

25%

10%

55%

10%

A. Multiplying the force you exert.

B. Multiplying the distance over which a force is exerted.

C. Changing the direction in which a force is exerted.

D. Reducing friction.

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

21 22 23 24 25 26 27 28 29 30 31 32

Input ForceThe force that you apply to

the machine.It is also known as the Effort

Force.

Output ForceThe force that is applied by

the machine.It is also known as the

Resistance Force.

A term that means the same thing as output force is

A. B. C. D.

0% 0%10%

90%

A. Input forceB. Resistance forceC. Effort forceD. Multiplying force

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

21 22 23 24 25 26 27 28 29 30 31 32