2. What is work?
• You work on math problems.
• You go to work.
• Making a sandwich is work.
• Taking out the trash is too much
work.
• Doing your homework is work.
• What machines help us work?
3. In physics, work is:
• *Work is a formula: W=Fd
• *W= Work; F= Force; d= distance
• *Example:
• *Moving an object with a force of one
newton for a distance of one meter=
one joule of work
• *A joule is a unit that measures work
5. Brainstorm using a circle map:
1. In the Center write: Work
2. In the circle write types of simple machines
3. In the frame of reference write down what
work these machines do
6. Input and Output
• *Input = how much force you put
into doing work
• *Output = how much work was
done
• *The work output can never
exceed the work input!
9. Efficiency
• *Efficiency is the fraction of
incoming energy that goes into a
process.
Examples: Fuel mileage,
appliances and energy efficiency
10. *Efficiency
• What does it mean to be efficient?
• *In a very efficient machine, all or
most of the work input becomes work
output
• In other words…if five joules of work
was used to lift a box, the box would
move the equivalent of five joules
output- nothing was wasted.
11. What about friction?
• *In the real world- Work Output is
always less than work input.
– WHY?
• *Forces like friction use up some of
the input work
– Example: wheel turning on an axle can
get very hot…when the wheel gets hot
some of that input work is being
converted to heat.
16. Power Demo
• These two people did the same amount of work.
•The difference is Power: One person used more
Power and got the work done much faster
•A more powerful machine does the same amount
of work in less time
18. Your Turn…
• On your paper:
– Look through Chapter 5, Section 1
Pg 85-90
– Add more information from this
section into your notes.
(at least six items)
19. Practice:
• Skill Sheet 5-A
Example:
• How much work is done on a 10 N block
that is lifted 5 meters off the ground by a
pulley?
Work = F x d
W = 10N x 5 meters = 50 newton- meters OR 50
joules
Remember: newton-meters = joules
20. Work
• Work = Force x Distance
• Work is only done when
something is moved a distance in
the direction of the force.
