# 1991 - WAEC Physics Past Questions & Answers - page 1

1
Which of the following is a fundamental quantity?
A
speed
B
density
C
lenght
D
impulse
CORRECT OPTION: c
2
A body moves with a constant speed but has an acceleration. this process if it
A
moves in a straight line
B
moves in a circle
C
is oscillating
D
is in equilibrum
CORRECT OPTION: b
3
A ball is projected horizontally from the top of a hill with a velocity of 20m-1. If it reaches the ground 4 seconds later, what is the height of the hill? (g = 10ms-2)
A
20m
B
40m
C
80m
D
160m
CORRECT OPTION: c
Initial horizontal velocity = 20ms-1

Initial vertical velocity = 0

s = ut + $$\frac{1}{2}gt^2$$ = 0 x 5 x 42

= 80m
4
A body moving with uniform acceleration has two points(5, 15) and (20, 60) on the velocity-times graph of its motion. Calculate
A
0.25ms-2
B
3.00ms-2
C
4.00ms-2
D
9.00ms-2
CORRECT OPTION: b
slope = acceleration

a = $$\frac{v_2 - v_1}{t_2 - t_1} = \frac{60- 15}{20 - 5}$$

= 3ms-2
5
the diagram above shows the position of a simple pendulum set in motion. At which of the positions does the pendulum have maximum kinetic energy?
A
5
B
4
C
3
D
2
CORRECT OPTION: c
6
An orange fruit drops to the ground from the top of a tree 45m tall. How long does it takes to reach the ground? (g = 10ms-2)
A
3.0s
B
4.5s
C
6.0s
D
7.5s
CORRECT OPTION: a
s = ut + $$\frac{1}{2}gt^2$$

45 = 0 + 5t2

t = 3s
7
power is defined as the
A
capacity to exert a force
B
product of force and time
C
product of force and distance
D
ability to do work
CORRECT OPTION: e
8
The product PV where P is pressure and V is volume has the same unit as
A
power
B
work
C
acceleration
D
impulse
CORRECT OPTION: b
P = $$\frac{N}{m^2}$$

V = m

PV = Nm unit of work
9
The diagram represents a block-and-tackle pulley system on which an effort of 50N is just able to lift a load of weight W. If the efficiency of the machine is 40%. find the value of W
A
300N
B
200N
C
140N
D
120N
CORRECT OPTION: d
Eff = $$\frac{MA}{VR}$$ x 100%

40 = $$\frac{MA}{60}$$

MA = 240

$$\frac{L}{E} = \frac{240}{100}$$

W = L = $$\frac{240}{100}$$ x 50

= 120N
10
A boatman facing north wants to cross a flowing river to a point directly opposite its position at the other bank. If the river is flowing eastwards, in what direction should he row his boat?
A
west
B
east
C
north-west
D
north-east
CORRECT OPTION: c
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