Question

You throw a dodge ball with a mass of 2.1 kg. The ball leaves your hand with a speed of 25 m/s. Identify the energy (PE or KE) and calculate it.

Answer 1

Given,

The mass of the object, m=2.1 kg

The speed of the object, v=25 m/s

Kinetic energy is the energy that an object possesses due to its motion. And potential energy is the energy that an object possesses due to its position.

The gravitational potential energy depends on the height of the object. As the change in the height of the object is not mentioned in the question, let us assume that there is no change in the potential energy.

The velocity of the object, however, changes. Thus the energy possessed by the object is the kinetic energy.

And the kinetic is given by

`E_K=(1)/(2)mv^2`

On substituting the known values,

`\begin{gathered} E_K=(1)/(2)*2.1*25^2 \\ =656.25\text{ J} \end{gathered}`

Thus the kinetic energy of the ball is 656.25 J