Question

Sophie throws a tennis ball down from a height of 1.5 m at an angle of 450 with respect to vertical. She drops another tennis ball from the same height. Use the Energy Interaction Model to predict which ball will hit the ground with greater speed.

Answer 1

Given that,

Height =1.5 m

Angle = 45°

We need to find the greater speed of the ball

Using conservation of energy

$P.E_{i}+K.E_{f}=P.E_{f}+K.E_{f}$

$mgh+\dfrac{1}{2}mv_{i}^2=mgh+\dfrac{1}{2}mv_{f}^2$

Here, initial velocity and final potential energy is zero.

$mgh=\dfrac{1}{2}mv_{f}^2$

Put the value into the formula

$9.8\times1.5=\dfrac{1}{2}v_{f}^2$

$v_{f}^2=2\times9.8\times1.5$

$v_{f}=\sqrt{2\times9.8\times1.5}$

$v_{f}=5.42\ m/s$

Hence, the greater speed of the ball is 5.42 m/s.