Waec Physics 1989 Past Questions and Answers

Question 31:

• WAEC 1989

What is the gravitational potential due to a molecule of mass, m and at a distance, r from it? (G = gravitational constant).

A. Gm²/r²
B. Gm/r
C. Gm²/r
D. G²m²/r
E. M²/Gr²

Question 32:

• WAEC 1989

Calculate the escape velocity for a rocket fired from the earth's surface at a point where the acceleration due to gravity is 10ms^-2 and the radius of the earth is 6 x 10⁶m.

A. 7.8 x 10⁶ms^-12
B. 1.1 x 10⁴ms^-1
C. 3.5 x 10⁷ms^-1
D. 6.0 x 10⁷ ms^-1
E. 1.2 x 10⁸ms^2-1

Question 33:

• WAEC 1989

The electric force between two point charges each of the magnitude, q at a distance of r apart in air of permittivity is:

A. Q²/4πεr
B. Rε₀/q²
C. 4πq/ε₀
D. Qr²/ε₀
E. Qε₀/4πε₀r²

Question 34:

• WAEC 1989

(a) What is meant by the statement: The linear expansivity of a solid is \(1.0 \times 10^{-5}K^{-1}\)?
(b)(i) Describe an experiment to determine the linear expansivity of a steel rod. (ii) Steel bars, each of length 3m at 29°C are to be used for constructing a rail line. If the linear expansivity of steel is \(1.0 \times 10^{-5}K^{-1}\), calculate the safety gap that must be left between successive bars if the highest temperature expected is 41°C.
(c) State three advantages and two disadvantages of thermal expansion of solids.

Question 35:

• WAEC 1989

(a) What is a wave motion?
The equation \(y = A \sin \frac{2\pi}{\lambda} (Vt-X)\) represents a wavetrain in which y is the vertical displacement of a particle at distance X from the origin in the medium through which the wave is travelling. Explain, with the aid of a diagram, what A and \(\lambda\) represent.
(b) (i) Describe an experiment to determine the frequency of a note emitted by a source of sound
(ii) A pipe closed at one end is 1 m long. The air in the pipe is set into vibration and a fundamental note is produced. If the velocity of sound in air is 340ms\(^{-1}\), calculate the frequency of the note
(c) State two differences between a sound wave and a radio wave.