10. CALCULATE: Find the amount of power used in each of the following examples. Show your calculations. a. You use a force of 10
N to move a box 100 m in 10 seconds. b. An athlete lifting weights does 900 J of work in 1 second. C. A truck does 30,000 J of work in 15 seconds. d. A fumiture mover uses a force of 150 N to push a large trunk 5 m across the floor in 5 seconds
1 answer:
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Answer:
a) -4 N
b) +4 N
Explanation:
Draw a free body diagram for each block.
For the large block, there are 2 forces: 12 N pushing to the right, and F pushing to the left.
For the small block, there is 1 force, F pushing to the right.
There are also weight and normal forces in the vertical direction, but we can ignore those.
Sum of forces on the large block in the x direction:
∑F = ma
12 − F = 4a
Sum of forces on the small block in the x direction:
∑F = ma
F = 2a
2F = 4a
Substitute:
12 − F = 2F
12 = 3F
F = 4
The small block pushes on the large block 4 N to the left (-4 N).
The large block pushes on the small block 4 N to the right (+4 N).
