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Physics Paper 2, May/June. 2010  
Questions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Main
General Comments
Weakness/Remedies
Strength
Question 11

(a) Distinguish between perfectly elastic collision and perfectly inelastic collision.
(b)Sketch a distance - time graph for a particle moving in a straight line with:
(i) uniform speed;
(ii) variable speed
 (c)A body starts from rest and travels distances of 120,300 and 180 m in successive equal time intervals of 12 s. During each interval the body is uniformly accelerated.
(i)Calculate the velocity of the body at the end of each successive time interval
(ii)Sketch a velocity-time graph for the motion.

Observation

Part (a). Performance was fair. Some of the respondent candidates failed to mention decrease in kinetic energy for the case of perfectly inelastic collision. Some candidates also failed to note that the question highlighted perfectly elastic collision and not ordinary elastic collision.
Part (b). Performance was high for (i), but low for (ii).
Part (c). This part was poorly tackled by candidates due to the use of wrong equations of motion and poor computational skills.
The expected answers are:
(a)Any 2 correct pairs

(c)(i) 1st stage of motion

x = ut + 1/2at2
120 = 0 x 12 + 1/2 X a x 122
a= 5/3
V1 = 5/3 x 12 = 20 ms-1

2nd stage of motion
x = ut + 1/2at2
300 =, 20 x 12 + ½ x a x 122
60 = 72a
a = 5/6

V = 5/6 x 12 = 10

V2= 10 + 20
= 30ms·1

3rd stage of motion

x = ut + 1/2at2
180 == 30 x 12 + ½ x a x 122
180 = 72 a
a = - 5/2
V = -5/2 x 12= -30
V3 = 30 + -30
= 0 ms·1

(ii)

Correct shape of each segment in relation to axes
Origin, (0.0) labeled
Only one axis labeled

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