Question

A “K-9 cannon” uses a powerful rubber band to launch a tennis ball(mass of 0.0577 kg) vertically upwards. The tennis ball has a velocity of 25.0 m/s as it leaves the barrel.
A. How long is the tennis ball in the air?

Answer 1

Answer:

t = 5.1[s]

Explanation:

To solve this problem we must first use the following equation of kinematics.

$v_{f}=v_{o} -g*t$

where:

Vf = final velocity = 0

Vo = initial velocity = 25 [m/s]

g = gravity acceleration = 9.81 [m/s²]

t = time [s]

Now replacing:

$0 = 25-9.81*t\\t=25/9.81\\t=2.54[s]$

Note: The key to understand this problem is that when the tennis ball is in the highest position its velocity is zero.

So it will take the same time from the highest point to the ground

t = 2.54 +2.54

t = 5.09 [s]