Work, scientifically speaking, is done on an object when a force is applied to move it a certain distance.

IMPORTANT! The distance (displacement) in this case is determined by measuring the difference from where the object started from to where it finishes, no matter what path it took. If a force is applied to move an object but there is no displacement, there is NO work done.

Displacement

2.0 m

3.0 m

3.0 m2.0 m

6.0 m

4.0 m

2.0 m3.0 m

Total Distance = 22.0 meters

Simple machines do NOT change the amount of

work done. Simple machines can make doing

work easier by lowering the magnitude of the force

applied by increasing the distance the force needs

to be applied over. Simple machine can also

change the direction of the force.

The work done is always the same!

2.0 N 10.0 Nm 5.0 m x =

NOTE: The distance in the formula is the distance the force is applied over, not the distance (displacement) of the object!

Usually Lowers

Doesn’t Change

Usually Increasesx =

1.0 N 10.0 Nm 10.0 m x =

0.5 N 10.0 Nm 20.0 m x =

1.Pulley 4. Screw

2. Inclined Plane 5. Wedge

3.Lever 6. Wheel and axle

Pulleys can either change the direction of the force or reduce the amount of force needed to do work by increasing the distance.

5.0 N

1.0 m

1.0 m

The magnitude and distance of applied force is the same. The direction is different!

F = 5.0 N

2.0 m

To use less force and still complete the same amount of work, a lower force must be applied over a greater distance.

5.0 N

1.0 m

F= 2.5 N

Inclined planes are the same as ramps.

8.0 m

2.0 m

10 N

Inclined planes make work easier by creating a longer distance for the object to travel while still accomplishing the same amount of work.

Without Ramp: Work = F x d = 10 N x 2.5 m = 20.0 Nm

Inclined planes are the same as ramps.

8.0 m

2.0 m

10 N

Inclined planes make work easier by creating a longer distance for the object to travel while still accomplishing the same amount of work.

With Ramp: Work = F x d = 2.5 N x 8.0 m = 20.0 Nm

LESS FORCE!

Inclined Plane

Inclined Planes

Load

Eff

ort

Fulcrum

2.0

m

2.0

m

Levers can change the direction of the force if the fulcrum is located in the middle of the lever arm.

LoadFulcrum

Eff

ort

2.0

m

6.0

m

Levers can also make work easier by lowering the force (effort) by increasing the applied distance.

Load

Effort

Fulcrum

Eff

ort

Load

Fulcrum

Fulcrum

LoadEff

ort

Wheel

Axle

Compound machines are machines that are

made of two or more simple machines.

Lever

Wedge

ScrewLever

Wheel & Axle

Pulleys

Lever

Lever

Wheel & Axle

Lever

Screw

Screw

Gear