Physics Test 134

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Physics Test 134

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Weekly Quiz Competition

Question 1
4 / -1

Work done by the system in closed path ABCA, as shown in figure is

A
Zero

B
(V₁ - V₂) (P₁ - P₂)

C

D

Solution

Work done = area of ΔABC
Question 2
4 / -1

A body executes S.H.M. of period 20 seconds. Its velocity is 5 cm s^-1, 2 seconds after it has passed the mean position. Find amplitude of the bob

A
21.45 cm

B
16.56 cm

C
19.67 cm

D
15.34 cm

Solution
Question 3
4 / -1

Calculate the gas constant for 1g of a gas from the following data: c_p = 0.245calg^-1oC^-1;c_v = 0.165calg^-1°C^-1

A
3.36 × 10⁶ erg g^-1 ^oC^-1

B
2.13 × 10⁶ erg g^-1 ^oC^-1

C
4.26 × 10⁶ erg g^-1 ^oC^-1

D
2.57 × 10⁶ erg g^-1 ^oC^-

Solution
Question 4
4 / -1

A balloon is moving upwards with a speed of 20 m/s. When it is at a height of 14 m from ground in front of a plane mirror in as shown in figure, a boy drops himself from the balloon. Find the time duration for which he will see the image of source S placed symmetrically before plane mirror during free fall.

A
1.7 s

B
1.9 s

C
2.6 s

D
2.1 s

Solution

The boy has dropped himself at point F. So, his velocity is 20 m/s in upward direction.
Let us first find the time to move from F to topmost point and then from topmost point to point C. From

Time taken to move the boy from Q to topmost point and then from topmost point to Q will be.

∴ Time required time is : t = t₁ - t₂ = 1.7 s
Question 5
4 / -1

Prism angle & refractive index for a prism are 60^o & 1.414. Angle of minimum deviation will be

A
15^o

B
30^o

C
45^o

D
60^o

Solution
Question 6
4 / -1

If a gas is heated at constant pressure then what percentage of total heat supplied is used for doing work ? (Given : γ for gas = 4/3)

A
25%

B
50%

C
75%

D
80%

Solution

Heat supplied dQ = nC_pdT
Heat used for work = dw = nRdT

= 25%
Thermodynamics Process
The process of change of state of a system involves change of thermodynamic variables such as pressure P, volume V and temperature T of the system. This process is known as thermodynamic process
Question 7
4 / -1

Four persons K, L, M, N are initially at the four corners of a square of side d. Each person now moves with a uniform speed v in such a way that K always moves directly towards L, L directly towards M, M directly towards N, and N directly towards K. The four persons will meet at a time .....

A
d/v

B
d/2v

C
2d/v

D
The four persons will never meet

Solution

The velocity of K throughout the motion towards the centre of the square is v cos45 and the displacement covered by this velocity will be KO.
Question 8
4 / -1

Estimate the speed of sound in air at standard temperature and pressure. The mass of 1 mole of air is 29.0 × 10^-3 kg

A
330.94 m s^-1

B
187.6 m s^-1

C
324.5 m s^-1

D
246.2 m s^-1

Solution

At N.T.P., P = 1.013 x 10⁵ N m^-2
volume of air, V = 22400 cm³ = 2.24 x 10^-2 m³
mass of 1 mole of air M = 29.0 x 10^-3 kg Therefore, density of air at N.T.P.,
Question 9
4 / -1

A pendulum bob is suspended on a flat car that moves with velocity v₀. The flat car is stopped by a bumper

(i) What is the angle through which the pendulum swings.

(ii) If the swing angle is θ = 60° and l = 10m, what was the initial speed of the flat car?

A

B

C

D

Solution

When the flat car collides with the bumper, due to inertia of motion the bob swings forward No work is done by tension of string on the bob therefore energy is conserved
Question 10
4 / -1

Two slits, 4 mm apart, are illuminated by light of wavelength 6000Å. What will be the fringe width on a screen placed 2 m from the slits?

A
0.12 mm

B
0.3 mm

C
3.0 mm

D
4.0 mm

Solution