Question

A disc of mass is kept floating in air with the help of bullets fired with the same velocity at the rate of bullets per second. Mass of each bullet is of the disc. If the bullets rebound with same speed in opposite direction after striking the disc, then the velocity of bullet at the time of impact is:

Answer 1

Answer:

Suppose speed of firing is V then after

rebounding the momentum frees fessed

to the dis will be charge in momentum

ΔP=−mv−(mv)=−2mv

↑

initial

Value =∣ΔP∣=2mv

⇒ Fr 10 bullets 10×2=20mv

m=0.05kg⇒∣ΔP∣total=v

time Δt=1 second

⇒ Fore entered =Δt∣ΔP∣total=1v=v Newton

it should balance the eight of disc

to prevent it from falling 

So =Mg=1×9.8

⇒v=9.8mls