PROBLEM
(II) A box of mass 4.0 kg is accelerated from rest by a force across a floor at a rate of 2.0 m/s2 for 8.0 s . Find the net work done on the box.
STEP 1
1. The box has a mass of 4.0kg.
2. The box starts from rest.
3. The box is accelerated at a rate of 2.0m/s2.
4. The acceleration occurs over a time period of 8.0s.
5. We need to find the net work done on the box.
STEP 2
1. Calculate the final velocity of the box.
2. Determine the displacement of the box.
3. Calculate the net work done using the work-energy principle.
STEP 3
Calculate the final velocity of the box using the formula for acceleration:
v=u+at where u=0m/s (initial velocity), a=2.0m/s2 (acceleration), and t=8.0s (time).
v=0+(2.0m/s2)(8.0s) v=16.0m/s
STEP 4
Determine the displacement of the box using the formula:
s=ut+21at2 Substitute u=0m/s, a=2.0m/s2, and t=8.0s:
s=0+21(2.0m/s2)(8.0s)2 s=21(2.0)(64.0) s=64.0m
SOLUTION
Calculate the net work done using the work-energy principle:
Wnet=ΔKE=21mv2−21mu2 where m=4.0kg, v=16.0m/s, and u=0m/s.
Wnet=21(4.0kg)(16.0m/s)2−21(4.0kg)(0)2 Wnet=21(4.0)(256.0) Wnet=512.0J The net work done on the box is:
512.0J
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