A body of mass 2 kg is thrown upward with an initial velocity of 20 m/s. After 2 seconds, its kinetic energy will be: (g = 10 m/s²)

Question

Question

This question was previously asked in

RRB ALP Previous Paper 2 (Held On: 9 Aug 2018 Shift 2)

Answer 1

Key Points

Kinetic energy is defined as the energy needed to move the body of mass m from one point to another with stated velocity v.
Using, Newton’s first equation of motion,

v = u + at

Where v = Final velocity of the body

As, body is moving upward, a = -g, where g = acceleration due to gravity

So, v = u – gt

Given, u = 20 m/s, t = 2 sec and g = 10 m/s²

On putting in the above formula, we get,

v = 20 – 10 × 2 = 0

Using, K.E. = ½ mv²

Where, K.E. = kinetic energy of the body

On putting the values, K.E. = ½ × 2 × 0 = 0 J

Therefore, the kinetic energy of the body of mass 2 kg is zero.