Question

You serve a volleyball with a mass of 2.1 kg. The ball leaves your hand with a speed of 30 m/s. How much energy does the ball have?

Answer 1

Given:

A volleyball with a mass of 2.1 kg leaves the hand with a speed of 30 m/s.

To find:

Total energy of the ball ?

Calculation:

First of all, let's assume that the ball is moving very close to the ground. Hence it's potential energy should be zero.

• However, the ball will possess kinetic energy by the virtue of its motion.

So, net energy :

$E_{net} = PE + KE$

$\implies E_{net} = 0+ \dfrac{1}{2} m {v}^{2}$

$\implies E_{net} = \dfrac{1}{2} \times 2.1 \times {30}^{2}$

$\implies E_{net} = 945 \: joule$

So, net energy of ball is 945 Joule.

Answer 2

Answer:

The energy of the ball is 945 Joule.

Explanation:

Given:

A volleyball with a mass of $2.1 \mathrm{~kg}$ leaves the hand with a speed of $30 \mathrm{~m} / \mathrm{s}$.

To find:

The total energy of the ball.

Consider that the ball exists moving very close to the ground. Hence its potential energy should be zero.

If the ball will possess kinetic energy by the virtue of its motion.

So, net energy or kinetic energy:

$&E_{n e t}=P E+K E$

$&\Longrightarrow E_{n e t}=0+\frac{1}{2} m v^{2}$

Kinetic energy $=\frac{1}{2} \times m\times v^{2}$

$=\frac{1}{2} \times 2.1 \times 30^{2}$

$=945 \text { joule }$

Therefore, the energy of the ball is 945 Joule.

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