Part (a) was well attempted. However, some candidates exhibited poor knowledge of the working principle of a filament bulb. Candidates taught the bulb will produce light before heat, whereas the filament if heated before it glows produces light.
Part (b) was fairly attempted. However, some candidates were stating why roads were banked at the bends rather than explaining why roads were banked at the bends.
In part (c), candidates were able to identify the forces F1 and F2 as well as explain the position where the bucket is heavier. However, most responding candidates failed to give the correct reason why the water does not pour out at position X.
In part (d), most candidates cannot relate mechanical energy to electrical energy hence were unable to calculate the current supplied by the battery. This showed poor knowledge of conversion of energies.
The expected answers are as follows:
(a) (i) Electric energy → mechanical energy → potential energy
OR Electrical energy → mechanical energy
(ii) Electric energy → heat energy → light energy
(b) At unbanked roads the frictional force required to keep a vehicle in a circular
path is not sufficient. Banking provides an additional force due to the normal reaction on the wheels to prevent the vehicle from slipping.
(c) (i) F1 = centripetal force
F2 = reactional/centrifugal force
- The bucket is heavier at position Y.
This is due to the direction of the centripetal force acting.
At position X, weight = mv2 - mg
r
At position Y, weight = mv2 + mg
r
(iii) The weight acts in the opposite direction to the tension.
The weight of the water is less than the centrifugal force.
- Efficiency = Power output
Power input
But Power output = force x distance
Time
Po = 600 x 10 x 5.0
80
= 375 W = 75 P1
100
Power input = 100 x 375 = 500W
75
P1 = IV
I = P1 V = 500 = 13.9A
36
