2013 - JAMB Physics Past Questions and Answers - page 2
11
What effort will a machine of efficiency 90% apply to lift a load of 180N if its efforts arm is twice as long as its load arm?
A
80N
B
90N
C
100N
D
120N
correct option: c
M.A. = \(\frac{Eff \times V.R.}{100}\)
M.A. = \(\frac{90 \times 2}{100}\)
M.A. = 1.8
E = \(\frac{L}{M.A.}\)
E = \(\frac{180}{1.8}\)
E = 100N
Users' Answers & CommentsM.A. = \(\frac{90 \times 2}{100}\)
M.A. = 1.8
E = \(\frac{L}{M.A.}\)
E = \(\frac{180}{1.8}\)
E = 100N
12
Calculate the work done when a force of 20N stretches a spring by 50mm.
A
0.5J
B
1.5J
C
2.0J
D
2.5J
correct option: a
W = \(\frac{1}{2}Fe\)
W = \(\frac{1}{2}\times 20 \times 0.05\)
W = 0.5J
Users' Answers & CommentsW = \(\frac{1}{2}\times 20 \times 0.05\)
W = 0.5J
13
At what depth below the sea-level would one experience a change of pressure equal to one atmosphere? Density of sea water = 1013kg-3, one atmosphere = 0.01 x 105Nm-2, g = 10ms-2
A
0.1m
B
1.0m
C
10.0m
D
100.0m
correct option: c
H = \(\frac{P}{e_g}\)
H = \(\frac{1.01 \times 10^5}{1013 \times 10}\)
H = 9.97
Users' Answers & CommentsH = \(\frac{1.01 \times 10^5}{1013 \times 10}\)
H = 9.97
14
What volume of alcohol will have same mass as 4.2m-3 of petrol?
Density of alcohol = 8.4 x 102kgm-3, density of petrol =7.2x103kgm-3
Density of alcohol = 8.4 x 102kgm-3, density of petrol =7.2x103kgm-3
A
0.8m3
B
1.4m3
C
3.6m3
D
49.m3
correct option: c
Mp = ep x Vp
Mp = 7.2 x 102 x 4.2 = 3024
VA = \(\frac{M}{e_A}\)
VA = \(\frac{3024}{8.4 \times 10^2}\)
VA = 3.6
Users' Answers & CommentsMp = 7.2 x 102 x 4.2 = 3024
VA = \(\frac{M}{e_A}\)
VA = \(\frac{3024}{8.4 \times 10^2}\)
VA = 3.6
15
Calculate the length which corresponds to a temperature of 20oC if the ice and steam points of an unguarded thermometer are 400 mm apart
A
20mm
B
30mm
C
60mm
D
80mm
correct option: d
At 100oC = 400
Therefore,
At 20oC = \(\frac{400}{100} \times \frac{20}{1}\) = 80
Users' Answers & CommentsTherefore,
At 20oC = \(\frac{400}{100} \times \frac{20}{1}\) = 80
16
A wire of length 100.0m at 30o has linear expansive of 2x10-5K-1 Calculate the length of the wire at a temperature of - 10oC
A
100.08m
B
100.04m
C
99.96m
D
99.92m
correct option: d
\(L_2 = L_1 + \alpha(\theta_2 - \theta_1)\)
= 100 + 0.00002(-10-30) = 99.92
Users' Answers & Comments= 100 + 0.00002(-10-30) = 99.92
17
A gas at a pressure of 105Nm-2expands from 0.6m-3 to 1.2m3 at constant temperature, the work done is
A
7.0 x 106J
B
6.0 x 10 6J
C
6.0 x 10 5J
D
6.0 x 10 4J
correct option: d
W = \(\frac{W_1 \times V_1}{V_2}\)
W = \(\frac{10 \times 0.6}{1.2}\)
W = 6.0 x 10 4J
Users' Answers & CommentsW = \(\frac{10 \times 0.6}{1.2}\)
W = 6.0 x 10 4J
18
Two liquids X and Y having the same mass are supplied with the same quantity of heat. If the temperature rise in X is twice that of Y, the ratio of specific heat capacity of X to that of Y is
A
2:1
B
1:2
C
4:1
D
1:4
19
Food cook quicker in salt water than in pure water because of the effect of
A
dissolved substances on the boiling point
B
atmospheric pressure on the boiling point
C
food nutrients on the thermal energy
D
salts on the thermal conductivity of water
correct option: a
Water impurities (such as salt water) boils at higher temperature than pure water. This helps to cook the food quicker.
Users' Answers & Comments20
Steam from boiling water causes more damage on the skin than does boiling water because
A
water has a high specific heat
B
steam has latent heat of fusion
C
the steam is at a highter temperature than the water
D
steam brings heat more easily by convection
correct option: c
Users' Answers & Comments