Question

What should be the mass of the bullet if its speed is 100 m/s and possesses kinetic energy of 0.1 KJ ?

Answer 1

Given:
Kinetic energy of a bullet, K.E=0.1KJ=0.1x 1000J=100J
speed=v=100m/s
If the mass of bullet is m then K.E
K.E=1/2mv²
m=2*K.E/v²
m=2x100/100x100=0.02kg

Answer 2

Kinetic energy of a bullet, K = 0.1 KJ
In SI system the unit of energy is joule and 1 KJ = 1000 J
∴ Kinetic energy    K = 0.1 KJ = 0.1 × 1000 = 100 J
and Speed             v = 100 m/s
∴ if mass of bullet is m ; the kinetic energy

                       K = 1/2 mv²


∴ Mass,          m = 2K / v²

                            = 2 × 100 / (100) ²


                             = 200 / 10000


                             = 2 /100

                             = 0.02 kg