INSTRUCTIONS:
This paper consists of Two sections: A and B
Section A: Attempt All questions (55 marks)
Section B: Choose any Three questions (45 marks)
Useful constants
Mass of electron: me  9.110 31 kg
Gravitational constant: G  6.67 10 11 Nm
2
Planck’ s constant: h  6.63 10 34 Js
Acceleration due to gravity: g  9.81m / s 2
Speed of light in vacuum: c  3.0 108 m / s
Coulomb’ s constant: k  9.0 109 Nm
Charge of an electron: e  1.6 10 19 C
2
C2
kg 2
1
2
3
4
5
6
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19) a) Find the ratio of Coulomb electric force FE to the gravitational force FG
between two electrons in vacuum.
(5marks)
b) Three charges are placed on three corners of a square, as shown in Fig.7. Each
side of the square is 30.0 cm. Compute the electric field E at the fourth corner.
What would be the force on a 6.0 C placed at the vacant post?
(10marks)
Fig.7
20)
a) Distinguish between elastic collision and perfect inelastic collision.(3marks)
b) Derive an expression to prove that the work done by an object is equal to
the change in kinetic energy. (3marks)
c) State the conditions for static equilibrium. (4marks)
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d) The horizontal beam in Fig. 7 weighs 150 N, and its center of gravity is at
(5marks)
its center. Find:
i.
The tension in the cable and
ii. the horizontal and vertical components of the force exerted on the beam
at the wall.
Figure 7
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