Question

A baseball of mass 1.23 kg is thrown at a speed of 65.8 mi/h. What is its kinetic energy?

Answer 1

Given:

The mass of the ball is

$m=1.23\text{ kg}$

The speed of the ball is

$\begin{gathered} v=65.8\text{ mi/h} \\ \end{gathered}$

Required: calculate the kinetic energy of the baseball

Explanation: to calculate the kinetic energy of a body we will use the formula as

$K.E=\frac{1}{2}mv^2$

first, we convert velocity from mi/h into m/s.

we know that

$1\text{ mi=1609.34 m}$

and

$1\text{ h=3600 sec}$

then the velocity is

$\begin{gathered} v=\frac{65.8\times1602.34\text{ m}}{3600\text{ s}} \\ v=29.29\text{ m/s} \end{gathered}$

now plugging all the values in the above formula, we get

$\begin{gathered} K.E=\frac{1}{2}mv^2 \\ K.E=\frac{1}{2}\times1.23\text{ kg}\times(29.29\text{ m/s})^2 \\ K.E=527.61\text{ J} \end{gathered}$

Thus, the kinetic energy of the baseball is

$527.61\text{ J}$