Paper 2 Conservation Laws in Physics Drills

Q1 Momentum in an Explosion

Two trolleys initially at rest push apart. Trolley A has mass $0.60\mathrm{kg}$ and moves left at $0.80\mathrm{m}{\mathrm{s}}^{-1}$. Trolley B has mass $0.40\mathrm{kg}$.

1. Calculate the velocity of trolley B. [3]
2. Calculate total kinetic energy after separation. [2]
3. Explain why kinetic energy can increase in this explosion. [2]

Q2 Charge Conservation at a Junction

At a circuit junction, currents $2.4\mathrm{A}$ and $0.70\mathrm{A}$ enter. Currents $1.5\mathrm{A}$ and $I$ leave.

1. Calculate $I$. [2]
2. State the conservation law used. [1]
3. Explain why charge does not build up at the junction in steady state. [2]

Q3 Nuclear Conservation

A nuclear equation is

$${}_{92}^{235}\mathrm{U}+{}_0^1\mathrm{n}\to {}_{56}^{141}\mathrm{Ba}+{}_{36}^{92}\mathrm{Kr}+x{}_0^1\mathrm{n}.$$

1. Use nucleon number conservation to find $x$. [2]
2. Check charge conservation. [1]
3. State one energy conservation point for fission. [2]