You reach out the second story window, which is 5 m above the sidewalk, and thro

Question

You reach out the second story window, which is 5 m above the sidewalk, and throw a 0.3 kg ball straight upward with 6 J of kinetic energy.

(a) What is the ball's gravitational potential energy when it is released?

__________J

(b) What is the ball's gravitational potential energy just before hitting the sidewalk?

__________J

(c) What is the ball's kinetic energy just before hitting the sidewalk?

_________J

(d) How would the answer to part c change if the ball had initially been thrown straight down with 6 J of kinetic energy? stay the same

decrease

increase

Explanation / Answer

a) GPE = m*g*h = 0.3*9.8*5 = 14.7 J

b) GPE = m*g*h = m*g*0 = 0 J

c) KEf = GPE(a) + KEi = 14.7 + 6 = 20.7 J

d) No change. Coming down, the ball will have the same velocity (with the sign reversed) as it had when thrown up.

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