Question

0.A 20-g bullet moving at 1 000 m/s is fired through a one-kg block of wood emerging at a speed of 100 m/s. What is the kinetic energy of the block that results from the collision if the block had not been moving prior to the collision and was free to move?

Answer 1

Answer:

KE = 0.162 KJ

Explanation:

given,

mass of bullet (m)= 20 g = 0.02 Kg

speed of the bullet (u)= 1000 m/s

mass of block(M) = 1 Kg

velocity of bullet after collision (v)= 100 m/s

kinetic energy = ?

using conservation of momentum

m u = m v + M V

0.02 x 1000 = 0.02 x 100 + 1 x V

20 = 2 + V

V = 18 m/s

now,

Kinetic energy of the block

$KE = \dfrac{1}{2}mv^2$

$KE = \dfrac{1}{2}\times 1 \times 18^2$

KE = 162 J

KE = 0.162 KJ