# 2007 JAMB Physics Past Questions & Answers - page 1

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1
The unit of moment of a couple can be expressed in?
A N m-1
B N m-2
C N m
D N m2

Correct Option: C

Solution
The unit of a couple is Newton-meter (N M)

2
A gramophone record takes 5s to reach its constant angular velocity of 4$$\pi$$ rads-1 from rest. Find its constant angular acceleration.
A 0.4$$\pi$$ rads-2
B 0.8$$\pi$$ rads-2
C 1.3$$\pi$$ rads-2
D 20.0$$\pi$$ rads-2

Correct Option: B

Solution
V = +at, and if it starts from N & T, U = 0
And for angular motion, W = O + at
4R = aχ5
∴ a = (4a)/5 = 0. 8$$\pi$$ rads-2

3
A car of mass 1500 kg goes round a circular curve of radius 50m at a speed of 40 ms-1. The magnitude of the centripetal force on the car is ?
A 4.8 x 104 N
B 4.8 x 103 N
C 1.2 x 103 N
D 1.2 x 102 N

Correct Option: A

Solution
Centipetal force of the car = ma = (MV)2/r
= (1500 x 40 x40)/50
= 48000 = 4.8 x 104 N

4
Two spheres of masses 5.0 kg and 10.0 kg are 0.3 m apart. Calculate the force of attraction between them?

[G = 6.67 X 10-11 Nm2 Kg2]
A 3.50 x 10-10N
B 3.71 x 10-8 N
C 3.57 x 10-2N
D 4.00 x 102N

Correct Option: B

Solution
The force of attraction between the two spheres is given by F (GM1 M2)/r2 = (6.67X 10-11 X5X10)/(0.3)2
= 3.71 X 10-8N.

5
A machine has a velocity ratio of 4. if it requires 800 N to overcome a load of 1600 N,what is the efficiency of the machine?
A 60%
B 50%
C 40%
D 2%

Correct Option: B

Solution
Efficiency = (M.A)/V.R X (100)/1
But M.A = (Load)/Effort = (1600)/800 = 2
Efficiency = (2)/4 x (100)/1 = 50%

6
A reservoir 500 m deep is filled with a fluid of density 850 kgm-3. If the atmospheric pressure is 1.05 x 105 Nm-2, the pressure at the bottom of the reservoir is.

[g = 10ms-2]
A 4.72 x 106 Nm-2
B 4.36 x 106 Nm-2
C 4.28 x 106 Nm-2
D 4.25 x 106 Nm-2

Correct Option: D

Solution
In general, pressure varies with depth in the relation p = lgh
= 850 x 10 x 500
= 4250000
= 4.25 x 106 NM-2

7
A piece of iron weights 250 N in air and 200 N in a liquid of density 1000 kgm-3. the volume of the iron is?
A 5.0 x 10-2 ms-2
B 4.5 x 10--2 ms-3
C 2.5 x 10-2 ms-8
D 2.0 x 10-2 ms-3

Correct Option: C

Solution
With in the air = 250N
wt. in the liquid = 200N
loss in wt. in the liquid = 250 - 200 = 50N
∴ Wt. the liquid of equal vol. of the iron = 50N
∴If the density of the liquid is 1000 lgm-3
then the volume of the liquid = (N)/D = V = (25kg)/1000 =0.025m3 = 2.5 x 10-2 m8.

8
A clinical thermometer is different from other mercury in glass thermometers owing to
A the constriction on its stem
B the grade of mercury used in it
C its long stem
D its wide range of temperatures

Correct Option: A

9
I. Use a liquid with a high melting point.
II. use a liquid of high volume expansivity.
III. use a capillary tube of large diameter.

which of the above best describes how the sensitivity of a liquid-in-glass thermometer can be enhanced?
A I only
B II. only
C I and II only
D II and III only

Correct Option: B

Solution
Using the liquid of high volume expansively II only

10
2 kg of water is heated with a heating coil which draws 3.5 A from a 200 V mains for 2 minutes. what is the increase in temperature of the water?

[specific heat capacity of water = 4200 jkg -1k-1]
A 30°
B 25°
C 15°
D 10°

Correct Option: D

Solution
Electricity heat energy supplies by the heater = lvt = 3.5 x 200 x (2 x 60) = 84000j.
and this heat is supplied to the 2 kg of the water MC ∆ t = 84000
2 x 4200 x ∆ t = 84000
∴ ∆t = (84000)/8400 = 10°c
∴ increase in temp. of water = 10°c

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