You started to decelerate the ball (i.e. ball become in contact with your hands)
ID: 1493596 • Letter: Y
Question
You started to decelerate the ball (i.e. ball become in contact with your hands) when it was 1 m above ground, and the ball came to a complete stop (velocity = 0) when it was 0.6m above ground, What was the potential, kinetic, and total mechanical energy of the ball when it came to a stop? (Height = 0.6 m, velocity = 0m/s) How much work did you do on the ball to bring it to a stop? What was the average force you exerted on the ball to bring it to a stop? In a few complete sentences, describe how the potential, kinetic, and total mechanical energy of the ball changed when it was free-falling from 15m to 1m. In a few complete sentences, describe how the potential, kinetic, and total mechanical energy of the ball changed from the time you made contact with the ball to the time the ball came to a complete stop.Explanation / Answer
d. P.E = mgh = m*9.8*0.6 = 5.88m J [ where m is mass of the ball]
K.E = 0.5mv^2 = 0 [ v = 0]
T.M.E = K.E. + P.E = 5.88 m J
e. Initial velocity at h = 1m = v
Loss in ke = 0.5*m*v^2
Loss in PE = mg(1 - 0.6) = 3.92m
Work done = 0.5mv^2 + 3.92m J [ where v is the initial velocity of the ball at hieght 1 m, and m is mass of the ball]
f. W = f.s
F = [0.5mv^2 + 3.92m]/0.4 = 1.25mv^2 + 9.8m J
g. When the ball was falling from 15 m to 1 m
2*9.8*(15-1) = v^2
v = 16.565 m/s
KE changed from 0 to 137.2m [where m is mas sof ball]
PE decreased from 137.2m to 9.8m
and total mechanical energy remained constant
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