1. Which of the following is the correct definition for work in science?
A) How much your brain hurts after a test in Chem/Phys
B) Where you go to make money
C) The amount of force applied over a distance

2. Which of the following units represent work?
A) Newton
B) Newton-meter
C) Joule
D) Meter

3. Draw the “Work Triangle”

4. Practice Problems
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
F= 10N
D= 5m
10N X 5m = 50 J

5. Practice Problems
A woman lifts her 100 N child up 1 meter and carriers her for a distance of 50 meters to her bedroom. How much work does the woman do?
100 N X 1 meter = 100J

6. Practice Problems
You pull your sled through the snow a distance of 500 meters with a force of 200 newtons. How much work did you do?
500 m X 200 N = 100,000J

7. Practice Problems
An ant sits on the back of a mouse. The mouse carries the ant across the floor for a distance of 10 meters. Was there work done by the mouse?

8. Practice Problem
A force of 2000 N is applied to a machine in order to lift a 1,000N load. What is the mechanical advantage of the machine?
2000N / 1000N = 2

9. Practice problems
A large wind turbine is able to transform 1,500,000 J of mechanical energy into 1,000,000 J of electrical energy every second. What is the efficiency of this turbine?
1,000,000 J / 1,500,000 J X 100 = 66%

10. Practice problems
You did 170 J of work lifting a 140 N backpack. How high did you lift the backpack?
170J/140N = 1.2 m

11. Practice Problems
A crane does 62,500 J of work to lift a boulder a distance m. How much did the boulder weigh?
62,500J / 25.0 m = 2500 N

12. Practice problems
An input force of 35 N is applied to a machine with a mechanical advantage of What is the size of the load this machine could lift (how large is the output force)?
0.75 X 35 N = 26.25N

13. Practice problem
If it requires 30 J of work to lift a bag of potatoes 2 m, how much does the bag of potatoes weigh?
30J / 2m = 15N

14. Practice problem
A 950 N skydiver jumps from a plane that is 3000m high. What is the total work performed on the skydiver?
950 N X 3000m = 2,850,000 J

15. Practice Problem
A fern receives 1055J of light energy and through photosynthesis, converts it to 8.3 J of energy to use for working plant system processes. What is the efficiency of the fern?
8.3J / 1055J X 100 = 0.8%