Physics 2011 | Study Mode

Question 11
A
80 J
B
500 J
C
300 J
D
120 J
Explanation
Efficiency = $$\frac{\text{work output}}{\text{work input}} \times \frac{100}{1}$$

= 40 = $$\frac{20 \times 10 }{x} \times \frac{100}{1}$$
= 500J

Question 12
A
I and II only.
B
II and III only.
C
I, II and III only.
D
I and III only.
Explanation
Pressure in liquid is independent of cross sectional area of the container/ liquid
the correct options are I & II

Question 13
A
kerosene
B
grease
C
water
D
petrol
Explanation
grease is more viscous than the rest of the liquids

Question 14
A
sound waves
B
light waves
C
D
x - rays
Explanation
Sound is the only mechanical wave among the rest which are electromagnetic waves.

Question 15
A
utra - violet rays
B
C
x - rays
D
infrared - rays
Explanation
r - rays has the highest frequency followed by X - rays, ultraviolet ray, visible light intra - red and the least is radio weaves

Question 16
A
conductor
B
black body
C
white body
D
red body
Explanation
Dull, black surface are good emitters or absorbers of energy

Question 17
A
atmosphere absorbs the sun's energy at night
B
earth radiates heat to the atmosphere at night
C
sun no longer shine at night
D
atmosphere reflects the sun's energy at night
Explanation
The earth radiate heat to the atmosphere at night thereby lowering the temperature of the ground

Question 18
A
30 s
B
10 s
C
10 s
D
15 s
Explanation
V = (2X)/t
330 = (2 x 4.95 x 103)/t
t = (9.9. x 103/330 = (9900)/330 = (90)/3
= 30 secs

Question 19
A
sublimation
B
condensation
C
coagulation
D
regelation
Explanation
Regelation means refreezing a phenomenon whereby melted ice free from increased pressure refreezed when they are released from the pressure.

Question 20
A
900 JK-1
B
90 JK-1
C
100 JK-1
D
200 JK-1
Explanation
Heat supplied = Heat gained Pt = MCD
30 x 5 x 60 = c x 10
where c = mc which is the heat capacity
c = (30 x 5 x60)/10 = 900 JKg-1

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