The hero of a stunt film fires 50 g bullets from a machine gun, each at a speed of 1.0 km/s. If he fires 20 bullets in 4 seconds. What average force does he exert against the machine gun during this period?

Explanation

The momentum of each bullet
`(0.05kg)(1000m/s)=50kg-m/s`
The gun is imparted this much of momentum by each bullet fired. Thus the rate of change of momentum of the gun
`((50 kg-m/s)xx20)/(4s)=250N`
IN order to hold the gun the hero must exert a force of 250 N against the gun.