UPSC General Science : Heat and Thermodynamics Notes Part 2

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Today’s Topic: Heat and Thermodynamics

Q1. If an iron ball and wooden ball have same radius are released from the same height in a vacuum. The time taken by both ball to reach the ground is:

a) Zero

b) Unequal

c) Iron ball take minimum and wooden ball take maximum time

d) Equal

Ans:    D

Explanation:    In the question given that the radius and the height are same and also as the both fall in the vacuum, therefore the time taken by both ball is exactly equal. When ball fall from a height time cannot be zero.

Q2. An object projected upward with velocity of 100m/s. It approximately what time will ball strike the ground?

a) 15 second

b) 20 second

c) 35 second

d) 10 second.

Ans:     B


When a body projected upward from the earth then

V= u + gt.

Here V= -100

[ ball goes upward]

g = 9.8m/s

[acceleration due to gravity]

So        V = u + gt

– 100 = 100 + 9.8 x t

t = 20 approx

Q3. The length of a second’s pendulum on earth (980xcm/s2) is 100cm. The length of it on a plant where g = 490 cm /s 2 would be:

a) 25 cm

b) 75cm

c) 300cm

d) 50cm

Ans:     D

Explanation:    Here,   t = 2π … for second’s

pendulum t = 28


l2 =  =

l2=20 cm.


Q4. Consider the following statements and select the correct answer /code:

1) Those substance which expand on freezing have their melting point lowered by the increases of pressure,. Whereas those substances which contract on freezing have their melting point raised by the increase of pressure.

2) The phenomenon that ice melt on application of pressure and again solidifies when the pressure released is known as regelation.

a) Only 1 is correct

b) Only 2 is correct

c) Only 1 and 2 are correct

d) Neither 1 nor 2 are correct.

Ans:     C

Explanation:    The substances that expand on freezing are ice, bismuth, antimony, wrought iron etc. Whereas substances which contract on freezing include wax, copper, etc.

Q5. Which one of the following represents the boiling point of water in Rankine scale:

a) 2720

b) 1680

c) 6720                

d) 3730

Ans:     C

Explanation:    In the Rankine scale, the boiling point of water is 6720 and freezing point is 4920, in Fahrenheit scale it is 2120 to 320, in centigrade scale00 minimum and 1000 maximum. In Reaumur scale it is 800 and 00 and in Kelvin scale 3730 to 2730, respectively. The relation between centigrade, Fahrenheit and Reaumur scale is

Q6. Consider the following statements and select the correct code:

1) Sphygmomanometer is a device used to measure blood pressure.

2) Manometer is a device for measuring differences in pressure usually by noting the differences in the height of two liquid column.

a) Only 1 is correct

b) Only 2 is correct

c) Both 1 and 2 are correct

d) Neither 1 nor 2 are correct

Ans:     C

Explanation:    A simple manometer is U-tube device form by bending a glass tube in the form of the letter U. If a pressure to be measured is fed one arm of the U-tube and other kept open to the atmosphere, the difference in the level of the liquid in the two arms gives a measure of the unknown pressure.

Q7. A cyclist turn round a curve at 15km/hour. If he/she turn at double the speed, the tendency of over turn is:

a) Unchanged

b) Quadrupled

c) Tripled

d) None of these

Ans:    B


If the cyclist turn at double of the speed the tendency of overturn is quadrupled. We noted that

tan θ =

There fore, when speed is doubled the tendency to overturn (2)2 = 4, i.e., quadrupled.

Q8. Which one of the following is the temperature at which the Celsius and the Fahrenheit reading are numerically equal but opposite is sign:

a) 690

b) 800/9

c) 970                   

d) 800/7

Ans:     D

Explanation:    We let X be the requiring reading



Or (X-32) X 5 = -9X

Or (5X – 160 = -9X

14X = 160

X = 80/7

Q9. When the moon passes between the sun and earth, solar eclipse occurs. People who are on the surface of earth just below the top of the moon’s Umbra will see which one of the following:

a) Diamond ring effect only

b) Annular solar eclipse

c) Total solar eclipse

d) None of the above

Ans:     B

Explanation:    These on the part of the earth, which is in Penumbra a partial solar eclipse is seen and to the observer on the part of earth which passes through umbra annular solar eclipse is visible.

Q10. In Which one of the following has the lowest refractive index:

a) Quartz

b) Diamond

c) Ice

d) Water

Ans:    C


The refractive index of given option is follow:

Quartz = 1.5

Diamond = 2.40

Ice = 1.31

Water = 1.33

Water = 1.00

Air = 1.00