neet physics tutor doubt 2 - NEET Physics Test: Mechanical Properties, Thermodynamics & Kinetic Theory

1. The uniform additional pressure applied on a

sphere is P. How much its temperature should be

raised to maintain its original volume? (The bulk

modulus of elasticity of the sphere is β and the

coefficient of volume expansion is α)

(1) Pα/β    (2) P/(3αβ)

(3) Pβ/α    (4) P/(αβ)

According to Hooke's law of elasticity, if stress is

decreased, the ratio of stress to strain (in elastic

limit)

(1) Decrease (2) Increase

(3) Remains same (4) Becomes zero

3. A metallic rod of length l and area of cross

section A is made of material having Young's modulus Y.

If the rod is elongated by an amount x and work done

is y, then which one of the following graphs is

correct?

For which of the following types of material

stress-strain curve is not a straight line within

elastic limit and strain produced is much large for

small stress applied?

(1) Brittle material

(2) Ductile material

(3) Elastomers

(4) Both (1) and (2)

5. Two wires A and B of diameter of cross section

0.5 cm each are loaded as shown in figure. The

unloaded length of wire A is 3 m and that of wire

B is 2 m. If Young's modulus of both wires is

same, then the ratio of elongation of wire A to

wire B will be

(1) 2:1    (2) 3:2

(3) 4:1    (4) 3:1

6. A metal wire 8 m long is suspended vertically.

How much does it stretch under its own weight?

(Density of material is 1600 kg/m°,

y = 4 × 10⁸ N/m³, g = 10 m/s²) (within elastic

limit)

(1) 6.4 mm (2) 1.28 mm

(3) 40 mm (4) 80 mm

7. The approximate depth of an ocean is 2000 m.

The compressibility of water is 40 × 10^-11 Pa^-1

and average density of water is 10³ kg/m³. The

fractional compression of water at the bottom of

the ocean will be (g = 10 m/s²)

(1) 2 × 10^-3 (2) 1 × 10^-3

(3) 8 × 10^-3 (4) 4 × 10^-3

8. A wire of length / is hanging from a fixed support.

The length changes to l and / when masses m.

and 2m are suspended separately from its free

end. Then / is equal to

(1) 211-12 (2) 11-12

(3) 11-212 (4) 311-212

If the interatomic spacing in steel wire is 4.0 A and

Young's modulus of steel Ysteel = 20 × 10¹⁰ N/m²

then force constant is

(1) 6 × 10^-3 N/A (2) 2 × 10-°N/Ä

(3) 8x 10-° N/A (4) 4 × 10^-3 N/A

10. A steel wire can support a maximum load of W

before reaching its elastic limit. How much load

can another wire, made out of identical steel, but

with double the radius of cross section as that of

the first wire, support before reaching its elastic

limit

(1) 2 W (2) W

(3) 8 W (4) 4 W

11. The area of cross-section of the wider limb shown

in figure is 500 cm². If a mass of 10 kg is placed

on the piston on the wider tube, the difference in

height h in the level of water in two tubes is

(ρ_water = 1000 kg/m³)

(1) 10 cm    (2) 20 cm

(3) 30 cm    (4) 15 cm

12. Consider the following statements

(a) With increase in temperature, viscosity of gas

increases

(b) With decrease in temperature, viscosity of

liquids increases

Correct statements are

(1) Only (a) (2) Only (b)

(3) Both (a) and (b) (4) Neither (a) nor (b)

13. The terminal velocity of copper ball of radius

2 mm falling through a tank of oil at 20°C is

6.5 cm/s. If viscosity of the oil at 20°C is

9.9 × 10^-1 kg m-' s-' and density of copper is

8.9 × 10³ kg m-3. Then density of the oil will be

(1) 1.2 × 10³ kg/m³ (2) 8.0 × 10² kg/m³

(3) 1.66 × 10³ kg/m³ (4) 1.8 × 10³ kg/m³

14. Figures (a) and (b) show a venturimeter tube

connected to the steady flow of a non-viscous liquid.

Which figure is correct regarding the static water

levels in the tubes?

(1) Only (a)    (2) Only (b)

(3) Both (a) and (b)    (4) Neither (a) nor (b)

15. The pressure at the bottom of a tank of water is

4P where P is the atmospheric pressure. If the

water is drawn out such that the level of water is

lowered by one third, the pressure at the bottom

of the tank will now be

(1) 2P/3    (2) 3P

(3) 4P    (4) 5P/3

16. The surface tension and vapour pressure of a

fluid at 20°C is 8 × 10^-2 N/m and 4 × 10³ Pa,

respectively. What is the radius of the smallest

spherical fluid droplet which can form without

evaporating at 20°C?

(1) 40 um (2) 4um

(3) 6.81×10-3m (4) 9x10-2m

17. The minimum force required to separate two

glass plate of area 1000 cm with film of water

0.1 mm thick between them, is (surface tension ol

water is 70 × 10^-3 N/m and angle of contact is 0°)

(1) 70 N (2) 50 N

(3) 140 N (4) 100 N

18. A cylinder of height 30 m is completely filled with

water. If water coming out through a small hole

hit the ground 30 m away from the bottom of the

cylinder. Then distance of the hole from the

bottom of the cylinder will be

(1) 10 m (2) 20 m

(3) 15 m (4) 5 m

19. A viscous fluid is flowing through a cylindrical

tube. The velocity distribution of the fluid is best

represented by which diagram?

20. Estimate the drop in temperature when a drop of

radius R breaks into N small droplets. (T: surface

tension, ρ: density, C: specific heat capacity)

(1) 3T/(ρCR)(N - 1)    (2) 2T/[ρCR(N - 1)]

(3) T/[ρRC(N - 1)]    (4) 2T/(ρRC)(N - 1)

21. A vessel of volume 0.04 m' contains a mixture of

hydrogen and helium at 20°C and 2 atmospheric

pressure and the mass of mixture is 10 g. Then

the ratio of mass of hydrogen to that of helium in

the mixture is nearly (1 atm = 105 Pa)

(1) 1:3 (2) 1:2

(3) 2:3 (4) 3:2

22. The coefficient of volume expansion of an ideal

gas at constant pressure at temp T K is equal to

(1) -1/T K^-1    (2) 1/T K^-1

(3) T K^-1    (4) 3/T K^-1

23. A cylinder of fixed capacity 67.2 litre contains

helium gas at standard temperature and

pressure. The amount of heat needed to raise the

temperature of the gas in the cylinder by 20°C will

be (R = 25/3 J mol^-1 K^-1)

(1) 250 J    (2) 750 J

(3) 400 J    (4) 900 J

24. Which of the following figures does not depict

ideal gas behaviour for a given amount of gas?

25. The root mean square speed of the molecules of

triatomic gas is V. When the absolute

temperature is tripled, the molecules dissociate

into three atoms, the new root mean square

speed of the atoms is

(1) V3V (2) V

(3) 3 V (4) 2 V

26. A fixed amount of an ideal monoatomic gas is

taken through the cycle ABCD as shown in the

figure. The efficiency of the cycle will be

(1) 22.2%    (2) 33.33%

(3) 20%    (4) 40%

27. For two mole of diatomic gas, work done at

constant pressure is W. The heat supplied at

constant volume for the same rise in temperature

of the gas is

(1) 3W/2    (2) 5W/2

(3) 2W    (4) W

28. Consider the process on an ideal gas as shown

in figure. The work done by the system is

(1) First positive then negative

(2) Always positive

(3) Always negative

(4) First negative then positive

29. If the heat input to a Carnot engine is four times

the work it performs, then the fraction of heat

rejected to the sink is

(1) 1/4    (2) 3/4

(3) 1/3    (4) 2/3

30. When a person jogs, he produces 15 kcal/min.

80% of this heat is removed as the sweat

evaporates. The amount of sweat evaporated per

minutes is (1 kg sweat requires approximately

580 kcal for evaporation)

(1) 1.6 g (2) 20.7 g

(3) 4g (4) 28 g

31. When one mole of gas expands as per the

relation V = KT23, where V is volume and T is

temperature. For the temperature change of

40 K. Work done is (R is universal gas constant)

(1) 35.6 R (2) 26.6 R

(3) 30.2 R (4) 20.1 R

32. The quantities of heat required to raise the

temperatures of two solid steel spheres of r and

2r respectively through 1 K each are in the ratio

of

(1) 1:4 (2) 1:8

(3) 1:1 (4) 8:27

33. The temperature of 200 g of water is to be raised

from 20°C to 60°C by adding steam at 100°C to

it. The mass of steam required for this purpose

nearly is

(1) 10 g (2) 14g

(3) 6 g (4) 18 g

34. It is difficult to cook rice in open vessel by boiling

it at high altitudes because of

(1) High boiling point due to low pressure

(2) Low boiling point due to low pressure

(3) Low boiling point due to high pressure

(4) High boiling point due to high pressure

35. Consider the P-V diagram for a fixed mass of an

ideal gas shown in figure. Choose the correct

corresponding pressure-density (P-ρ) diagram.

36. The increase in moment of inertia I of a uniform

rod, having thermal coefficient of linear expansion

α, about an axis passing through its one end and

perpendicular to its length when its temperature

is slightly increased by ΔT is

(1) IαΔT    (2) IαΔT/2

(3) 2IαΔT    (4) 3IαΔT

37. Ends of a rod A of length / having thermal

conductivity K is maintained at temperature Ty

and T2 (T,>T2). The thermal current through the

rod is Q. Now another rod B of same length and

area of cross section as that of rod A and having

thermal conductivity 2K is welded together side

by side and common ends of the combination is

maintained at temperature T, and T2. The new

thermal current through the combination will be

(1) Q (2) 2Q

(3) (4) 3Q

38. Choose the correct graph which represents Wien's

displacement law. Symbols have their usual meanings.

(4) Both (1) and (3)

39. If l is the distance between lower fixed point and

upper fixed point of thermometer and X is the

length of the mercury column above the lower

fixed point for temperature t°C, then value of t will

be

(1) 100X/l    (2) 50X/l

(3) X/l    (4) 50l/X

40. The rate of cooling of a body is

(1) Independent of the nature of the surface of

the body

(2) Independent of the area of the body

(3) Independent of the temperature of the

surrounding

(4) Depend on the excess of temperature of the

body above that of surrounding

41. In which of the following phenomena, the heat

travels along straight line with speed of light

(1) Thermal radiation

(2) Thermal conduction

(3) Natural convection

(4) Forced convection

42. Hot water cools from 60°C to 50°C in the first 10

minutes and to 42°C in next 10 minutes. Then the

temperature of the surrounding is

(1) 10°C

(2) 30°C

(3) 20°C

(4) 15°C

_43. Two spherical black bodies have radii r and 9r.

Their surface temperature are T, and T2. If they

- radiates same power then value of T1 is

(1) 1:9 (2) 3:1

(3) 4:1 (4) 1:8

44. According to Stefan's law, the power radiated by a black body at absolute temperature T is P.

If its absolute temperature is doubled to 2T, then the power radiated will become

(1) 2P    (2) 4P

(3) 8P    (4) 16P

45. The power radiated by a black body is P and it

radiates maximum energy around the wavelength

λ₀. If the temperature of the black body is now

changed so that it radiates maximum energy

around the wavelength 3λ₀/4, the power radiated

by it will increase by factor of

(1) 256/81    (2) 64/27

(3) 16/9    (4) 4/3