Question

5. A ball of mass 200g kept at a height has 90 J of energy and is allowed to
fall. The velocity with which it strikes the ground is *​

Answer 1

Given :

• Mass of the body = 200 g or 0.2 kg.

• Energy possessed by the body = 90 J

To find :

The velocity of the body with which it will reach the ground.

Solution :

Since we have to find the velocity of the ball and we know the relation ,

⠀⠀⠀⠀⠀⠀⠀⠀⠀The kinetic energy possessed by a body is directly proportional to square of the velocity of the body.

Mathematically,

⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀KE ∝ V²

We know the formula for Kinetic energy of a body i.e,

Kinetic energy :

∴ KE = ½mv²

Where :

• KE = Kinetic energy possessed by the body.
• V = Velocity of the body.
• m = Mass of the body.

Now by using the formula for Kinetic energy of a body and substituting the values in it, we get :

==> KE = ½mv²

==> 90 = ½ × 0.2 × v²

==> 90 × 2 = 2/10 × v²

==> 180 = 1/5 × v²

==> 180 × 5 = v²

==> 900 = v²

==> √900 = v

==> 30 = v

∴ v = 30 m/s.

Hence the velocity of the body is 30 m/s.