State what is meant by a perfectly elastic collision.

State what is meant by:

(ii) A completely inelastic collision.

A stationary uranium nucleus disintegrates, emitting an alpha-particle of mass $6.65\times {10}^{-27} \mathrm{kg}$ and another nucleus $\mathrm{X}$ of mass $3.89\times {10}^{-25} \mathrm{kg}$.

Using the symbols $v_{\alpha }$ and $v_x$ For velocities, write an equation for the conservation of momentum in this disintegration.

A stationary uranium nucleus disintegrates, emitting an alpha-particle of mass $6.65\times {10}^{-27} \mathrm{kg}$ and another nucleus $\mathrm{X}$ of mass $3.89\times {10}^{-25} \mathrm{kg}$.

  Calculate the ratio $v_{\alpha }:v_x$ after the disintegration.

(a) State two quantities that are conserved in an elastic collision.

(b) A machine gun fires bullets of mass $0.014 \mathrm{kg}$at a speed of $640{ \mathrm{ms}}^{-1}$.

(i) Calculate the momentum of each bullet as it leaves the gun.

(b) A machine gun fires bullets of mass $0.014 \mathrm{kg}$at a speed of $640{ \mathrm{ms}}^{-1}$.

(ii) Explain why a soldier holding the machine gun experiences a force when the gun is firing.

(b) A machine gun fires bullets of mass $0.014 \mathrm{kg}$at a speed of $640{ \mathrm{ms}}^{-1}$.

(iii) The maximum steady horizontal force that a soldier can exert on the gun is $140 \mathrm{N}$. Calculate the maximum number of bullets that the gun can fire in one second.

Two railway trucks are travelling in the same direction and collide. The mass of truck $\mathrm{X}$ is $2.0\times {10}^4 \mathrm{kg}$ and the mass of truck $\mathrm{Y}$ is $3.0\times {10}^4 \mathrm{kg}$. This graph shows how the velocity of each truck varies with time.

(b) State and explain whether the collision of the two trucks is an example of an elastic collision.