Question

compute the speed of 2 kg ball having kinetic energy 4 J

Answer 1

Here,
m=2 kg
K.E.=4 J
now,
K.E.=4 
 or  =4
or 1/2*2*v^2=4
or v^2=4
or v^2=2 m/s  ans.

Answer 2

Given,

The mass of a ball = 2 Kg

The kinetic energy of the ball = 4 J

To find,

The speed of the ball.

Solution,

We can simply solve this numerical problem by using the following process:

Let us assume that the speed of the ball is x m/s.

Mathematically,

The kinetic energy of a moving body

= 1/2 × (mass of the body) × (speed of the body)^2

{Statement-1}

Now, according to the question;

The kinetic energy of a moving body = 4 J

=> 1/2 × (mass of the body) × (speed of the body)^2 = 4 J

=> 1/2 × (2 Kg) × (speed of the body)^2 = 4 J

=> (speed of the body)^2 = 4 J

=> speed of the body = √4 m/s = √(2^2) m/s = +2 m/s

{Since the measure of speed can never be negative}

=> speed of the body = 2 m/s

Hence, the speed of the ball is equal to 2 m/s.