Waec Physics 1997 Past Questions and Answers

Question 46:

• WAEC 1997

In a nuclear reaction, the mass defect is 2 x \(10^{-6}\)g. Calculate the energy released given that the velocity of light is 3 x \(10^{8}ms^{-1}\)

A. 9 x \(10^{7}\)J
B. 1.8 x \(10^{8}\)J
C. 1.8 x \(10^{9}\)J
D. 9 x \(10^{-10}\)J
E. 3.6 x \(10^{11}\)J

Question 47:

• WAEC 1997

An atom radiates 1.5 x \(10^{-19}\)J of energy when an electron jumps from one energy level to another. What is the wavelength of the emitted radiation? (Planck’s constant =6.6 x \(10^{-34}\)Js. Speed of light in air=3 x \(10^{8}ms^{-1}\)

A. 1.32 x \(10^{-6}\)m
B. 2.98 x \(10^{-6}\)m
C. 3.32 x \(10^{-6}\)m
D. 6.82 x \(10^{-6}\)m
E. 8.01 x \(10^{-6}\)m

Question 48:

• WAEC 1997

(a) Explain the term work
(b) Draw a diagram of a pulley system with a velocity ratio of 5.
(c) A man pulls up a box of mass 70kg using an inclined plane of effective length 5m onto a platform 2.5m high at uniform speed. If the frictional force between the box and the plane is 100N, draw the diagram of all the forces acting on the box when in motion and calculate the
(i) minimum effort applied in pulling up the box
(ii) velocity ratio of the plane
(iii) mechanical advantage of the plane
(iv) efficiency of the plane
(v) energy lost in the system
(vi) work output of the man
(vii) total power developed by the man given that the time taken to raise the box onto the platform is 50s. (g = 10ms\(^{-2}\)).

Question 49:

• WAEC 1997

(a) Explain the term resonance and give two examples
(b)(i) Describe, with the aid of a labelled diagram, an experiment to show how the frequency of the note emitted by a vibrating string depends on the length of the string.
(ii) State two precautions necessary to obtain an accurate result.
(c) A sonometer wire is plucked and it vibrates emitting a fundamental note. State the effect on the frequency of the note if the
(i) tension in the wire were made nine times as large with no change in the length of the wire;
(ii) length of the wire were doubled with no change in the tension.

Question 50:

• WAEC 1997

(a) Sketch the form of the magnetic flux pattern due to a current flowing
(i) in a long solenoid
(ii) through two long straight parallel wires when the directions of the current are opposite. (Neglect the earth's magnetic field).
(b) Draw a labelled diagram of an electric bell and explain how it works
(c) An electric bell takes a current of 0.2A groin a battery of two dry cells connected in series. Each cell has an e.m.f. of 1.5V and an internal resistance of 1.0\(\Omega\).
(i) Calculate the effective resistance of the bell
(ii) What current would the bells take in the cells were arranged in parallel?