GET IT DONE

1
GET IT DONE!

• Take a calculator if you need one!!!
• IN YOUR OWN WORDS write down a definition for
  work.
• Congratulations! You have just turned 16 and
  received your driving permit. On your first trip
  out, you are unlucky enough to get a flat tire!
  As a first time driver you do not have a jack to
  change the tire. Frustrated you push and push on
  the car in an effort to lift it. Do you think
  you are doing work as you try to lift the car?
  Why?

2
Work, Power, and Machines OH MY!!!!!

• Section 9.1

3
Things to know and study!

• Define work and power.
• Be able to calculate work done on an object the
  rate work is done.
• Use mechanical advantage to explain how machines
  make doing work easier.
• Calculate the mechanical advantage of various
  machines.

4
What is Work???

• Work a quantity that measures the effects of a
  force acting over a distance
• This means - the object being worked on must
  undergo a change in motion for work to be done.
• Equation for work (put on equation card)
• W ? F x d
• work ? force x distance
• (Joules, J) (N) (m) ? units
• 1 N?m 1 J 1 kg?m2/s2

5
Lets Practice!

• Q A father is playing with his daughter by
  lifting her repeatedly in the air. How much work
  does he do with each lift, assuming he lifts her
  2.0m and exerts an average force of 190 N.
• A force, F ? 190N distance, d ? 2.0m work,
  W ? ?
• W ? F ? d
• W ? 190N ? 2.0m ? 380 N?m ? 380 J
• Please try 1-3 on Pg. 285 ) Thanks!

6
What is Power???

• Power the rate at which work is done
• This means it is a measure of how much work is
  done in a certain amount of time.
• Equation for power (put on equation card)
• P ? W
• t
• Power ? work (J)
• time (s)
• Power is measured in watts, W
• 1 W ? 1 J/s

7
Lets Practice!!

• Q It takes 100,000J of work to lift an elevator
  18m. If this is done in 20s, what is the average
  power of the elevator during the process?
• A work, W ? 100,000J time, t ? 20s power,
  P ? ?
• P ? W ? t
• P ? 100,000J ? 20s ? 5,000J/s ? 5,000W
• Please try 1-3 on Pg. 287 ) Thanks!