Physics Test 206

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Physics Test 206

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Question 1
4 / -1

If the velocity v of a particle moving along a straight line decreases linearly with its displacement s from 20 ms⁻¹to a value approaching zero at s = 30 m, then acceleration of the particle at s = 15 m is

A
2/3 m s⁻²

B
-2/3 m s⁻²

C

D

Solution
Question 2
4 / -1

When a rubber-band is stretched by a distance x, it exerts a restoring force of magnitude F = ax + bx², where aa and bb are constants. The work done in stretching the unstretched rubber-band by L is :

A
aL²+ bL³

B
½(aL²+ bL³)

C

D

Solution
Question 3
4 / -1

A square surface of side L metres is in the plane of the paper. A uniform electric field (volt/m), also in the plane of the paper, is limited only to the lower half of the square surface (see diagram). The electric flux in SI units associated with the surface is

A
EL²

B
EL²/2ε₀

C
EL²/2

D
Zero

Solution

The lines are parallel to the surface.

And thus electric field lines donot cross the area of the paper.
Question 4
4 / -1

An elastic wire is stretched by 3 cm from its natural length and its potential energy is V. If the wire is stretched by 6 cm from its natural length, its potential energy will be

A
V

B
2V

C
3V

D
4V

Solution
Question 5
4 / -1

During adiabatic change, specific heat is

A
zero

B
greater than zero but finite

C
less than zero

D
infinite

Solution

In an adiabatic process, ΔH = 0

Hence, zero is the correct answer.
Question 6
4 / -1

Two rods (one semi-circular and other straight) of the same material and of same cross-sectional area are joined as shown in the diagram. The points A and B are maintained at different temperatures. The ratio of the heat transferred through a cross-section of a semi-circular rod to the heat transferred through a cross-section of the straight rod in a given time is

A
2 : π

B
1 : 2

C
π : 2

D
3 : 2

Solution
Question 7
4 / -1

A cylindrical solid of length L and radius a is having varying resistivity given by ρ = ρ₀x where ρ₀ is a positive constant and x is measured from the left end of the solid. The cell shown in the figure is having emf V and negligible internal resistance. The electric field as a function of x is best described by:

A

B

C

D
None of these

Solution

Consider an elemental part of solid at a distance xx from left end of width dxdx .

Resistance of this elemental part is,
Question 8
4 / -1

If K₁ and K₂ are maximum kinetic energies of photoelectrons emitted when lights of wavelength λ₁ and λ₂ respectively incident on a metallic surface. If λ₁ = 3λ₂, then

A

B

C
K₁ = 3K₂

D
K₂ = 3K₁

Solution
Question 9
4 / -1

A lens is made of flint glass (refractive index = 1.5). When the lens is immersed in a liquid of refractive index 1.25, the focal length

A
Increases by a factor of 1.25

B
Increases by a factor of 2.5

C
Increases by a factor of 1.2

D
Decreases by a factor of 1.2

Solution
Question 10
4 / -1

Three concentric spherical shells have radii a, b and c (a < b < c) and have surface charge densities σ, −σ and σ respectively. If V_A, V_B and V_C denote the potentials of the three shells, then, for c = a+b, we have

A
V_C = V_B ≠ V_A

B
V_C ≠ V_B ≠ V_A

C
V_C = V_B = V_A

D
V_A = V_C > V_B

Solution