A 10G bullet is short from a 5kg gun with a velocity of 400m/s.What is the speed of recoil of the gun?

3 answers

Please type your subject in the School Subject box. Any other words, including obscure abbreviations, are likely to delay responses from a teacher who knows that subject well.
Initial momentum = 0
momentum of bullet = mv
momentum of gun = MV

Using conservation of momentum
mv+MV = 0
therefore
V=-mv/M
The momenta of the bullet and the gun are equal (and opposite in direction) after firing. If Vr is the recoil velocity,

5.0*Vr = 0.01 * 400

Solve for Vr, which will be im m/s.

Note that I had to use the same mass units for bullet and gun.