A gun of mass 10kg fires a bullet of mass 240g at a speed of 300ms-1. What is the speed of the gun's recoil?
First, convert the mass of the bullet into SI units -> 240g=0.24kg
The law of the conservation of momentum states that m1v1=m2v2. To find the speed of the gun, rearrange for v1 to give v1=m2v2/m1 and substitute in the given values; m2=0.24kg, v2=300ms-1, and m1=10kg. This gives v1=0.24x300/10=7.2ms-1
