1. Work, force, motion, and power
12/ /16
Using mathematical formulas
Solving word problems

2. Learning Objectives: Students will be able to 1
Learning Objectives: Students will be able to 1. recognize units of measure and correctly apply them to mathematical problems 2. apply mathematical equations to describe the relationships between force, work, and power

3. Force, Work, Power A force is a push or a pull
Work is a force acting over a certain distance
Power how quickly work is done

4. PROBLEM 1 (sample) How much work is done by a person who uses a force of 30 Newtons to move a grocery cart 3 meters?
Given (know):
Need to know:
Formula:
Substitute:
Compute:
Final Answer:

5. Know (Given): Force = 30 Newtons Distance = 3 meters
Sample PROBLEM How much work is done by a person who uses a force of 30 Newtons to move a grocery cart 3 meters?
Know (Given):
Force = 30 Newtons
Distance = 3 meters

6. Need to know: Work = ? Joules
Sample PROBLEM How much work is done by a person who uses a force of 30 Newtons to move a grocery cart 3 meters?
Need to know:
Work = ? Joules

7. Sample PROBLEM How much work is done by a person who uses a force of 30 Newtons to move a grocery cart 3 meters?
Formula Needed:
Work = Force x Distance

8. _____ Joules = 30 Newtons x 3 meters
Sample PROBLEM How much work is done by a person who uses a force of 30 Newtons to move a grocery cart 3 meters?
Substitute:
_____ Joules = 30 Newtons x 3 meters

9. Sample PROBLEM How much work is done by a person who uses a force of 30 Newtons to move a grocery cart 3 meters?
Compute:
30 x 3 = 90

10. Final Answer: Work = 90 Joules
Sample PROBLEM How much work is done by a person who uses a force of 30 Newtons to move a grocery cart 3 meters?
Final Answer:
Work = 90 Joules

11. Problem Solving Process
Given:
Force = 30 Newtons
Distance = 3 meters
Need to Know:
Work = ? Joules
Formula:
Work = Force x Distance
Substitute
?J = 30N x 3m
Compute
30 x 3 = 90
Final Answer:
Work = 90 Joules

12. Problem 2a:
How much work is done by a person who uses a force of 40N to move a grocery cart 4 meters?
Need to know:
Formula:
Substitute:
Compute:
Final Answer:

13. problem 2b.
How much work is done if the person pushes with the same force (40N), but the grocery cart moves 0 meters?
Know:
Need to know:
Formula:
Substitute:
Compute:
Final Answer:

14. Problem 3
5000 J of work is done to lift a rock 50 meters. How much force is applied?
Know:
Need to know:
Formula:
Substitute:
Compute:
Final Answer:
By lifting this rock you are increasing its _________________ energy.

15. Problem 4
A teacher does 200 joules of work in 10 seconds. How much power did he use?
Know:
Need to know:
Formula:
Substitute:
Compute:
Final Answer:
He could have increased power by increasing the amount of ________________ or decreasing the amount of ______________.

16. Problem 5 (Page 78, Question 3)
How much power, in watts, is needed to cut a lawn in 50 minutes if the work involved is 100,000 Joules?
(* Must convert _____________ to ______________)
Know:
Need to know:
Formula:
Substitute:
Compute:
Final Answer:

17. Problem Solving Process
Given:
Time = 50 minutes
Work = 100,000 Joules
Need to Know:
Power = ? Watts
Formula:
Power = Work/Time
Substitute:
100,000 J / 50 minutes = ? Watts
Compute:
50 minutes x 60 seconds/1 minute = 3000 seconds
100,000/3,000 = 34
Final Answer:
Power = 34 Watts

18. More Practice:
Page 78 # 1-7
Page 96 #11,12,13
Page 98 # 1,7,9