Safe policing
Grabbit and Grubbit (Solicitors to the Common Man) Ltd are proposing to take a case to the European Court claiming that the use of rubber bullets is a violation of Human Rights. Their grounds are that, for the same mass and speed, the momentum in a rubber bullet is the same as that in a lead one. Thus they do the same damage on impact and are therefore equally likely to be lethal.
How will you prepare a case for the Government’s defence?
Solution
Reveal

Solution
Assume that both bullets are stopped inside the body. If they have the same initial momentum,
the change will be the same for both and so is the impulse

If this still does not convince you, consider the impact of a car:
- [a)] on a concrete wall, and
- [b)] on a stack of tyres.
Experience tells you that the first case is more likely to be fatal for the driver than the second. What matters here is the degree of "inelasticity" of the collision and not whether the car hits the wall or "the wall hits the car". After all the force exerted by the wall on the car is the same as the force exerted by the car on the wall changed in sign.