Work is defined as energy transferred by a force causing an object to move. The formula for work is W=Fxd. Power is the rate at which work is done and is calculated as P=W/t. Machines make work easier by changing the amount or direction of force applied. Simple machines include levers, pulleys, wheels and axles, inclined planes, wedges, screws, and compound machines which combine simple machines. Mechanical advantage is the number of times a machine multiplies force while efficiency is the ratio of work output to work input.

1. Work
• Work is energy transferred that causes
the object to move in the direction of the
force — no movement, no work.
• Formula for work: W = F x d
• Units:
– Work – joule (J)
– Force – newton (N)
– Distance – meter (m)

2. Power
• Power is the rate at which work is done
• (determines work over time)
• Formula: P = W/t
• Units:
– Power – watt (W)
– Work – joule (J)
– Time – seconds

3. Machines
• Machine – device that makes work easier
by changing the amount of force (effort) or
direction of the force
• Changing force (effort) is mechanical
advantage
• Machines let you swap force for distance
or distance for force….you still do the
same amount of work

4. Levers – move from a fixed point

5. Pulleys – grooved wheel that holds
rope or cable

6. Wheel and axle – 2 circular objects
of different sizes (wheel is larger)

7. Inclined plane – straight slanted
surface

8. Wedge – two inclined planes that
move

9. Screw – inclined plane wrapped
around a cylinder

10. Compound machine – made of
more than one simple machine

11. • Mechanical advantage – number of times
a machine multiples force
• Work output – work done by the
machine; product of output force and the
distance of the force applied
• Work input – work done on a machine;
product of the input force and the distance
of the force applied
• Mechanical efficiency – ratio of output to
input of energy or power (divide output by input)

12. • Due to friction, work put into a machine is
always greater the than the work output by
the machine.