Question

A ball of mass 2kg is thrown up with a speed of 10m/s . Find the kinetic energy of the ball at the time of throwing. Also find the potential energy of the ball at the highest.

Answer 1

Given mass = 2 kg

Velocity = 10 m/s

kinetic energy is highest at the throwing

Here,

kinetic energy = ½ × 2 × 10 × 10

= 100 J

now,

highest kinetic energy= highest pottential energy

and

pottential energy is maximum at its highest point

so,

pottential energy = 100 J

pottential energy = 100 JKinetic energy = 100 J

Answer 2

Given:

Mass of the ball $=2kg$

Velocity of the ball $=10m/s$

To find:

1. Kinetic energy while throwing up
2. Potential energy at the highest point.

Solution:

Step 1

We have been given that a ball of mass $2kg$ is thrown with an initial velocity of $10m/s$ .

The kinetic energy for the ball will be given by

$KE=\frac{1}{2}mv^{2}$

Substituting the given values, we get

$KE=\frac{1}{2}(2)(10)^{2}$

$KE=100J$

Hence, the kinetic energy of the ball while throwing up is 100 J.

Step 2

Now,

When the ball is thrown up, the acceleration acting on the ball will be the acceleration due to gravity.

Hence, the height reached by the ball will be given by,

$v^{2}- u^{2}=2as$

We have,

$u=10m/s$   $;$ $v=0m/s$  

We get

$(0)^{2}- (10)^{2} =2(-10)h$

$h=\frac{100}{20}$

$h=5m$

Step 3

Now,

The potential energy of the ball at the highest position will be

$PE=mgh$

We have,

$m=2kg$   $;$  $g=10m/s^{2}$    $;$  $h=5m$

We get,

$PE=2(10)(5)$

$PE=100J$

• We can infer that whole of the kinetic energy at the beginning of the throw is converted into potential energy so that the ball is able to reach the height This is called Law of conservation of energy or energy transfer.

Final answer:

Hence,

1. The kinetic energy of the ball while throwing the ball up is 100 J.
2. The potential energy of the ball at the highest position is 100 J.