A massive tractor rolls down a country road. in a perfectly inelastic collision, a small sports car runs into the machine from behind. (i) which vehicle experiences a change in momentum of larger magnitude

The answer for this change in the magnitude of momentum is the same for both because momentum is always conserved so both vehicles have the identical change.

So for determining who has the greater change in kinetic energy, momentum (P) = mv so P^2 = m^2 v^2 P^2 / 2m = 1/2 m v^2 = energy So the weightier the mass the smaller the energy change for the same momentum change so in here, the car has a greater change in kinetic energy.