Question

Give two explanations of why a bullet will have a greater velocity from a rifle than a shorter pistol. This may help (http://www.learner.org/vod/vod_window.html?pid=553)

Answer 1

a bullet fired from a rifle will have greater velocity as compared to bullet fired from a pistol
let the mass of gun be M, mass of bullet be m
then for same energy E produced in the explosion
let speed of bullet be v and that of guns be u
then from conservation of moemntum
mv = Mu

also, 0.5mv^2 + 0.5Mu^2 = E

0.5(Muv + Mu^2) = 0.5*M*u(v + u) = E
so for constant E, decreasing M will increase value of v
hecne bulets fored from rifles are faster as they have more mass ( for same energy produced in the explosion)