Question

A body of mass 2 kg is thrown up vertically with a kinetic energy 490J.If the acceleration due to gravity is 9.8m/s2, the height at which the kinetic energy of the body becomes half of original value is a)50m b)25m c)12.5 d)10

Answer 1

Mass of the body = 2 kg

Initial kinetic energy = 490

Let the height be h from the ground when the kinetic energy becomes half.

Hence, the increase in the potential energy = 490 - 245 = 245 J

Increase in potential energy = 245 J

mgh = 245

$h = \frac{245}{m \times g}$

$h = \frac{245}{2 \times 9.8}$

h = 12.5 m

Hence, the height at which the kinetic energy becomes half is 12.5 m.

Hence, the option (c) is correct.