Question

If we throw a body upwards with velocity of 4 m/s, at what height its kinetic energy reduce to half of the initial value?

Answer 1

At half of the height the kinetic energy will reduce to half.

Explanation:

Given, initial velocity (u) =4m/s

And final velocity (v) =0

Also, Acceleration due to gravity (g) = -9.8m/s sq,

So, v sq.=u sq. -2gh

0 = 4m/s * 4m/s - 2*9.8m/ s sq.*h

Therefore, 16=9.8h

h = 0.625m

Let the mass be '1kg'

And initial velocity = 4m/s (Given)

So.,Initial kinetic energy =1/2*1*4*4=8J

K.e is 8J at 0.625m height

When k.e is reduced to half i.e 8J. Then clearly the height will be 0.3125m i.e the half of 0.625m.

Hence,at half height the kinetic energy will reduce to half.

Hope, it will help you.