1990 - WAEC Physics Past Questions & Answers - page 1

1
Which of the following instruments is suitable for making the most accurate measurement of the internal diameter of a test tube?
A
metre rule
B
A pair of callipers
C
A micrometer screw gauge
D
A tape rule
CORRECT OPTION: b
2
A particle of mass 2.5 x 10-6kg revolving around the earth has a radial acceleration of 4 X 107 ms-2. What is the centripetal force of the particles?
A
6.25 x 10-14N
B
1.60 x10-13N
C
5.00 x 10N
D
1.00x102N
CORRECT OPTION: d
F = ma = 2.5 x 10-6 x 4 x 107 = 100N
3
An oscillating pendulum has a velocity of 2ms-1 at the equilibrium position O and velocity at same point P. Using the diagram above, calculate the height of P above O. (Take g = 10ms2)
A
5.0m
B
2.0m
C
0.4m
D
0.2m
CORRECT OPTION: d
Kinetic energy at O = P.E at P 1/2mV = mgh
h = v/2g = 0.2m
4
Which of the following are contact forces? I. Force of tension II. Force of fiction, III. Magnetic force III Force of reaction.
A
I,II and III only
B
I, II and IV only
C
I, III and IV only
D
II, III and IV only
CORRECT OPTION: b
5
A plane inclined at an angle at 30o to the horizontal has an efficiency of 50%. The force parallel to the plane required to push a load of 120 N uniformly up the plane is
A
40√3N
B
60N
C
120N
D
200N
CORRECT OPTION: c
E = M.A/V.R ; 50/100 = M.A/2
M.A = 1; L/E = 1
E = L = 120N
6
The diagram above represents a portion of a micrometer screw 20 gauge. What is its reading?
A
3.70mm
B
3.67mm
C
3.50mm
D
3.33mm
CORRECT OPTION: e
7
A girl whose mass is 55kg stands on a spring - weighing machine inside a lift. When the lift starts to ascend, its acceleration is 2ms1. What will be the reading on the machine? (Take g = ms-2)
A
66 kg
B
55 kg
C
44 kg
D
22 kg
CORRECT OPTION: a
Reading = mg + ma = m(g + a) = 55(10 + 2)
= 660N = 66kg
8
Two forces each of 4 N act on the opposite sides of a rectangular plate as shown in the diagram above. Calculate the magnitude of g the couple acting on the plate.
A
6.4 Nm
B
3.2 Nm
C
1.6 Nm
D
0.8 Nm
CORRECT OPTION: c
couple moment = F x d = 4 x 0.4 = 1.6Nm
9
A force F is applied to a body P as shown in the diagram above. If the body P moves through a distance r, which of the following represents the work done?
A
Fx
B
Fcosθ/x
C
Fx tanθ
D
Fx sinθ
CORRECT OPTION: e
10
An object R leaves a platform XY with a horizontal velocity of 7m-1 and lands at Q. lf it takes the same object 0.3s to fall freely from Y to P, calculate the distance PQ.(Take g = 1Oms2)
A
7.30m
B
2.55m
C
2.10m
D
1.65m
CORRECT OPTION: c
D = v x t = 7 x 0.3 = 2.1m
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