Physics Test 67

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Physics Test 67

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Weekly Quiz Competition

Question 1
4 / -1

A uniform rope of length 10 m and mass 3 kg hangs vertically from a rigid support. A block of mass 1 kg is attached to the free end of the rope. A transverse pulse of wavelength 0.05 m is produced at the lower end of the rope. The wavelength of the pulse when it reaches the top of the rope is:

A
0.10 m

B
0.12 m

C
0.16 m

D
0.18 m

Solution
Question 2
4 / -1

An ideal monoatomic gas is taken around the cycle ABCDA as shown in the P-V diagram. The work done during the cycle is:

A
PV

B
0.5 PV

C
2 PV

D
3 PV

Solution

As we know, work done in a process is equal to the area under the curve in the P-V graph.

Work done during the cycle = Area ABCDA

= BA × DA

From the diagram,

BA = 2V - V = V

DA = 2P - P = P

= V × P = PV

Hence, the correct option is (A).
Question 3
4 / -1

A thin equiconvex lens of glass of refractive index μ₂=1.5 separates two media of refractive indices μ₁=1.4 and μ₃=1.6, as shown in the figure:

A
A The lens will neither converge nor diverge the parallel beam

B
The lens will diverge the parallel beam of light

C
The lens will converge the parallel beam of light

D
The lens will act like a prism

Solution

By the relation between n, u, v, and R for refraction at a spherical surface,

Thus, the lens will neither converge nor diverge the parallel beams.

Hence, the correct option is (A).
Question 4
4 / -1

"Good emitters are good absorbers" is a statement concluded from:

A
Newton's law of cooling

B
Stefan's law of radiation

C
Provost's theory

D
Kirchhoff's law

Solution

According to Kirchhoff's law, the ratio of emissive power to absorptive power is the same for all surfaces at the same temperature and is equal to the emissive power of a perfectly black body at that temperature.

e₁/a₁ = e₂/a₂=…[E/A] perfectly black body

Thus, since (Eλ)black is constant at a given temperature, this implies that good absorber is a good emitter (or radiator).

Hence, the correct option is (D).
Question 5
4 / -1

A machine gun fires a bullet of mass 40 g with a velocity 1200 ms⁻¹. The man holding it can exert a maximum force of 144N on the gun. How many bullets can he fire per second at the most?

A
3

B
2

C
4

D
1

Solution

A man fired bullet n times in t seconds of mass M=m×n

Now we have been given a force of 144 N.

Apply the concept of Impulse,

I=F⋅Δt= change in momentum =Mv

Here, M=m×n

F.Δt=mnv

Put value in the above equation, we get

144×1=0.04×n×1200

Solve for n, where n= number of bullets fired in one second.

144/1200×0.04 = n

The number of bullets fired per second is,

n=3

Hence, the correct option is (A).
Question 6
4 / -1

Find the minimum attainable pressure of an ideal gas in process T=T0+αV², where T₀ and α are positive constants and V is the volume of one mole of gas assuming d²P / dT²=+ve.

A
2R

B
3R

C
3R

D

Solution

Hence, the correct option is (A).
Question 7
4 / -1

According to Maxwell's hypothesis, changing electric field gives rise to:

A
Magnetic field

B
Pressure gradient

C
Charge

D
Voltage

Solution

From Maxwell's Electromagnetic theory, the Electromagnetic Wave propagation contains electric and magnetic fields vibrating perpendicularly to each other. Thus, changing of electric field gives rise to magnetic field.

Then the Maxwell's equation,

∇×B=μ₀ (J + ϵ₀ dE/dt)

Using this equation of maxwell we can say changing electric field dE/dt induces magnetic field.

Hence, the correct option is (A).
Question 8
4 / -1

An unpolarised beam of intensity I₀ is incident on a pair of nicol prisms making an angle of 60^∘ with each other. The intensity of light emerging from the pair is:

A
I₀

B
I₀/2

C
I₀/4

D
I₀/ 8

Solution
Question 9
4 / -1

The engine of a car produces an acceleration of 6 ms⁻² in the car. If this car pulls another car of the same mass, then the acceleration would be:

A
6 m/s²

B
12 m/s²

C
3 m/s²

D
1.5 m/s²

Solution

Given,

Acceleration, a=6 ms⁻²

By the Newton's second law,

F = ma

Force applied by engine =6m

When two cars are pulle,

(m+m)a=6m

⇒2ma=6m

⇒a=3 ms⁻²

⇒2ma=6m

⇒a=3 ms⁻²

Hence, the correct option is (C).
Question 10
4 / -1

If w₁,w₂ and w₃ represent the work done in moving a particle from A to B along three different paths 1,2 and 3 respectively(as shown)in the gravitational field of a point mass m. Find the correct relation between w1,w₂ and w₃.

A
w₁ > w₂ > w₃

B
w₁ = w₂ = w₃

C
w₁ < w₂ < w₃

D
w₂ < w₁ < w₃

Solution

Gravitational force is a conservative force. Work done in moving object under that force only depends upon initial and final positions and not on the path along which it travels.

∴ w₁=w₂=w₃

Hence, the correct option is (B).