work

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.