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?

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 = 162 J

KE = 0.162 KJ

hi there!

out of the two, (b) precision would be more reasonable.   however, both a and b could be pretty reasonable.

-awesomerepublic   : )