Physics Paper 2, MAy/June. 2013
 Questions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Main

Weakness/Remedies
Strength

Question 2

The horizobtal component of the initial speed of a particle projected at 30o to the horizontal is 50 ms-1. If the acceleration of free fall due to gravity is 10 ms-2 determine its:

1.   Initial speed;
2.  Speed at the maximum height reached.

_____________________________________________________________________________________________________
Observation

Majority of the responding candidates got the initial speed but many of them could not determine the speed (u) at the maximum height reached because ux = 50ms-1 was wrongly substituted. Candidates failed to realize that at the maximum height the horizontal component of the projectile equal that of its initial velocity since ? = 0. Hence they could not establish the correct relationship between initial velocity (u) and ux. The expected answers are: (a) Let u represent the initial velocity of particle and ux the horizontal component. ux = u cos 30o = 50 u = 50 cos 30 = 57.7 ms-1 (b) Let v represent its velocity at the maximum height. ALTERNATIVELY At the maximum height v = vvx2 + vy2 vy = 0 vx = ux = 50ms-1 = v 502 + 02 = 50ms-1