HELP Question 1 of 25
A boy throws a ball straight up with a speed of 21.5 m/s. The ball has a mass
of 0.19 kg. How much gravitational potential energy will the ball have at the
top of its flight? (Assume there is no air resistance.)
O A. 48.5J
B. 41.2J
O C. 43.9 J
O D. 37.5J

Explanation:

Although there is absolutely NO regard for significant digits, I can help you with this, nonetheless.

The equation for Potential Energy is PE = mgh. We have everything but the height of the ball. We have to solve for that using a one-dimensional motion equation:

v² = v₀² + 2aΔx, where Δx is our displacement (the height we need for PE). Filling in and keeping in mind that at the max height of parabolic travel, the final velocity of the object is 0:

0 = (21.5)² + 2(-9.8)Δx and

0 = 462.25 - 19.6Δx and

-462.25 = -19.6Δx so

Δx = 23.58 m. Using this as the h in our PE equation:

PE = .19(9.8)(23.58) so

PE = 43.9 J, choice C.

pe = weightxheight = 2000x1000=2,000,000joules