# 1993 - JAMB Physics Past Questions & Answers - page 1

1
Which of the following quantities has the same unit as the watt?
A
Force x time
B
Force x distance
C
Force x acceleration
D
Force x velocity
CORRECT OPTION: d
2
The external and internal diameter of a tube are measured as (32 ± 2)mm and (21 ± 1)mm respectively. Determine the percentage error in the thickness of the tube.
A
27%
B
14%
C
9%
D
3%
CORRECT OPTION: c
Actual thickness = 34 - 22 = 12

error thickness = 30 - 20 = 10

error = 12 - 10 = 2mm that is, (11 ± 1)mm

%error = $$\frac{1}{11}$$ x $$\frac{100}{1}$$

= 9%
3
Two forces of magnitudes 7N and 3N act at right angles to each other. The angle $$\theta$$ between the resultant and the 7N force is given by
A
cos$$\theta$$ = $$\frac{3}{7}$$
B
sin$$\theta$$ = $$\frac{3}{7}$$
C
tan$$\theta$$ = $$\frac{3}{7}$$
D
cot$$\theta$$ = $$\frac{3}{7}$$
CORRECT OPTION: c
$$\theta$$ = tan-1$$\frac{3}{7}$$
4
A rocket burns fuel at the rate of 10kgs-1 and ejects it with velocity of 5 x 103ms-1. The thrust exerted by the gas on the rock is
A
2.5 x 107N
B
5.0 x 104N
C
5.0 x 102N
D
2.0 x 10-3N
CORRECT OPTION: b
Thrust = $$\frac{\text{mass x velocity}}{time}$$

= 10 x 5 x 103

= 5.0 x 104N
5
The force experienced by an object of mass 60.0kg in the moon's gravitational field is 1.002 x 102N. What is the intensity of the gravitational field?
A
0.60Nkg-1
B
1.67Nkg-1
C
6.12 x 102Nkg-1
D
9.81ms-2
CORRECT OPTION: b
Intensity = $$\frac{1.002 \times 102}{60}$$

= 1.67Nkg-1
6
Which of the following correctly describes the energy changes in the generation of light by a hydroelectric power station?
A
Electrical $$\to$$ mechanical $$\to$$ potential
B
potential $$\to$$mechanical $$\to$$electrical $$\to$$ light
C
mechanical $$\to$$ sound $$\to$$ electrical $$\to$$ light
D
kinetic $$\to$$ mechanical $$\to$$ electrical $$\to$$light
CORRECT OPTION: b
7
A plane inclined at angle $$\theta$$ has a velocity ratio of 10 : 1. The inclination of the plane to the horizontal is given by
A
tan$$\theta$$ = $$\frac{1}{10}$$
B
cot$$\theta$$ = $$\frac{1}{10}$$
C
cos$$\theta$$ = $$\frac{1}{10}$$
D
sin$$\theta$$ = $$\frac{1}{10}$$
CORRECT OPTION: d
V.R = $$\frac{1}{sin\theta}$$

= 10

sin = $$\frac{1}{10}$$
8
A weightless vessel of dimensions 4m x 3m x 2m is filled with a liquid of density 1000kgm-3 and sealed. What is the maximum pressure this container can exert on a flat surface? [g = 10ms-2]
A
9 x 104NM-2
B
4 x 104NM-2
C
3 x 104NM-2
D
2 x 104NM-2
CORRECT OPTION: d
P = 2 x 1000 x 10

= 2 x 104NM-2
9
An object of mass 400g and density 600kgm-3 is suspended with a sting so that half of it is immersed in paraffin of density 900kgm-3. The tension in the string is
A
1.0N
B
3.0N
C
4.0N
D
5.0N
CORRECT OPTION: b
volume of object = $$\frac{400 \times 10^{-2}}{600}$$

= 0.00067m3

volume of paraffin displaced = $$\frac{1}{2}$$ x 0.00067

= 0.00034m3

mass of paraffin = 900 x 34 x 10-5

= 0.3kg

weight of paraffin = 0.3 x 10

= 3N = upthrust = tension in the string
10
The thermometric properties of the thermocouple is that is
A
e.m.f. changes with temperature
B
resistance changes with temperature
C
volume changes with temperature
D
pressure changes with resistance
CORRECT OPTION: a
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