### CIE A Level Physics Solved Past Paper Oct/Nov 2017 P23

1 bii) P=kAT^4 can be written in the form y=constant*x^2 because x-axis is x^2 and y-axis is P so a graph of y=x^2 is always an increasing gradient graph with positive slope.

2 bi) Since the solid sphere is moving with constant velocity, all forces acting on it in different directions must be balanced.

ci) The pressure at the surface of any liquid (when x=0.17m above the base of container) is due to atmosphere.

3 bi) The total momentum before collision along the y-axis is zero and that after the collision is due to ball A that moves upwards and ball B which moves down so it will have its momentum with negative magnitude.

ii) The total momentum of balls A and B before the collision along the x-axis will be equal to that after the collision. Total momentum before the collision is all due to ball A and is 4v and that after the collision is due to both balls since they both are moving in the same direction along the x-axis after head-on collision. Ball A moves with momentum 4*(6cos(theta)) towards the right and ball B moves with 12*(3.5cos(35)) of momentum towards the right. **YOU HAVE TO BE VERY CAREFUL WITH SIGNS WHEN DEALING WITH MOMENTUM CONSERVATION.**

iii) If kinetic energy is not conserved during collision then that collision is not elastic. Total momentum is always conserved regardless of whether a collision is elastic or inelastic.

4 ci) Point Y is nearer to the observer standing at point O than point X is so intensity or amplitude of sound heard from point Y is going to be a lot higher than that from point X.

ii) The car moves from X to Y so frequency of sound heard from point Y is going to be higher. Relationship between frequency and wavelength is inverse proportionality so a higher frequency observed from point Y means sound has its minimum wavelength at point Y.

5c) Although force due to electric field on alpha particle is double the force on the proton, its mass is also 4 times higher thus it accelerates at half a rate than a proton does.

6d) There will be no effect on current that flows through filament wire (because no change to the charge) but resistance will be a lot less this time when temperature falls with decrease in p.d. since resistance is directly proportional to temperature.