IB Physics Heat and Internal Energy

A tutorial sheet on the heat and internal energy follows.

1. An system gains an amount Q of heat energy. Does the internal energy increase by this amount?
2. An air conditioner extracts an amount Q of heat energy from a room. Is the work done by the air conditioner Q?
3. A heat engine has a heat inflow Q1 per cycle and a heat outflow of Q2 each cycle. What is the efficiency of this engine?
4. Must a heat engine always have a clockwise cycle on a p-V diagram?
5. Does a heat pump always have an anticlockwise cycle on a p-V diagram?

IB Physics "Show that" Collision Questions

A tutorial sheet of show that problems follows. Show all working and explain the Physics principles being used. Assume that all speeds are much less than the speed of light.

1. A mass m moves at a speed u. A mass M is at rest. A one dimensional elastic collision occurs. Show that the speed of M after the collision is 2mu/(m+M).

2. A paticle P of mass m moving at a speed u strikes a particle of mass nm that is at rest. If the collision is elastic show that the ratio of the final velocity of P to its initial velocity is (1-n)/(1+n).

3. A particle is at rest on a smooth horizontal surface. It is struck off centre by a particle of equal mass moving at a speed u. The collision is elastic. Show that the velocity vectors of the particles are perpendicular after the collision.

4. A particle of mass M is at rest on a smooth horizontal surface. It is struck by a particle of mass m moving at a speed u, the angle between the line of cetres of the particles and the initial velocity vector being 45° . The collision is elastic. Show that after collision the angle made by the velocity vector of m (measured in the laboratory reference frame) with its initial direction is given by tanθ = M/m