Question

A tennis ball of mass m = 0.059 kg is thrown straight up with an initial speed v0 = 14 m/s. Let the gravitational potential energy be zero at the initial height of the tennis ball. Part a) What is the maximum height, h in meters, the ball reaches? Part b) What is the work done by gravity, Wg in Joules, during the ball's flight to its maximum height?

Answer 1

a)

Using conservation of energy:

`\begin{gathered} E1=E2 \\ (1)/(2)mvi^2+mghi=(1)/(2)mvf^2+mghf \\ where: \\ hi=0 \\ vi=14m/s \\ vf=0 \\ so: \\ vi^2+0=0+2ghf \end{gathered}`

Solve for hf:

`\begin{gathered} hf=(vi^2)/(2g) \\ hf=(14^2)/(2(9.8)) \\ hf=10m \end{gathered}`

b)

`\begin{gathered} W=F_g\cdot d \\ W=9.8\cdot10 \\ W=98J \end{gathered}`