Two forces, of magnitudes F 1 = 80.0N and F 2 = 30.0N, act in opposite direction
ID: 1381258 • Letter: T
Question
Two forces, of magnitudes F1 = 80.0N and F2 = 30.0N, act in opposite directions on a block, which sits atop a frictionless surface, as shown in the figure. (Figure 1)Initially, the center of the block is at position xi = -6.00cm . At some later time, the block has moved to the right, and its center is at a new position, xf = 6.00cm .
a)Find the work W1 done on the block by the force of magnitude F1 = 80.0N as the block moves from xi = -6.00cm to xf = 6.00cm .
b)Find the work W2 done by the force of magnitude F2 = 30.0N as the block moves from xi = -6.00cm to xf = 6.00cm .
c)What is the net work Wnet done on the block by the two forces?
d)Determine the changeKf?Ki in the kinetic energy of the block as it moves from xi = -6.00cmto xf = 6.00cm .
Explanation / Answer
net force in opoosite driections Fnet = F1-F2
Fnet = 80-30 = 50 N
total distance moved = xf-(-xi) = 6+6 = 0.12 m
so
part A:
net Work done W = Fs
W1 = 80 * 0.12
W1 = 9.6 N
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W2 = Work done by F2 = 30 * 0.12 = 3.6 N
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Net Work Done W = (80-30) * 0.12
W net = 6 N
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from Work eenrgy therorem
Wnet = change in KE = 6 N
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