Physics Test 130

Result

Physics Test 130

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Question 1
4 / -1

A metal wire PQ slides on parallel metallic rails having separation 0.25 m, each having negligible resistance. There is a 2Ω resistor and 10V battery as shown in figure. There is a uniform magnetic field directed into the plane of the paper of magnitude 0.5 T. A force of 0.5N to the left is required to keep the wire PQ moving with constant speed to the right. With what speed is the wire PQ moving? (Neglect self-inductance of the loop)

A
8 m/s

B
16 m/s

C
24 m/s

D
32 m/s

Solution
Question 2
4 / -1

In the given figure a ring of mass m is kept on a horizontal surface while a body of equal mass 'm' attached through a string, which is wounded on the ring. When the system is released the ring rolls without slipping. Consider the following statements and choose the correct option.

(i) acceleration of the centre of mass of ring is g/3

(ii) acceleration of the hanging particle is 2g/3

(iii) frictional force (on the ring) acts along forward direction

(iv) frictional force (on the ring) acts along backward direction

A
statement (i) and (ii) only

B
statement (ii) and (iii) only

C
statement (iii) and (iv) only

D
none of these

Solution

Free body diagram of ring and mass is

Since the ring is in pure rolling so its above point acceleration will be 2a and similarly acceleration of mass will be 2a.
The equation of motion of the system is
mg – T = m(2a) ......(1)
T = ma .......(2)
Substitute the value of T in equation (1)
mg - ma = 2ma
3ma = mg
a = g/3
So the acceleration of the center of the ring is, g/3
And acceleration of the hanging mass is 2a = 2g/3
Question 3
4 / -1

A concave mirror gives a real image magnified 6 times when the object is moved 6 cm the magnification of the real image is 4 times. What will be the focal length of the mirror?

A
31.2 cm

B
42 cm

C
23 cm

D
-36 cm

Solution

As we know that the magnification
Question 4
4 / -1

A spring mass system with unequal masses is placed at rest on a smooth horizontal surface. The spring is initially kept compressed with a thread. When the spring is cut, the mass m moves so as to enter in a vertical circular loop of radius r. The minimum compression x in the spring so that the mass m may negotiate the vertical loop is

A

B

C

D

Solution

Let x be the compression in the spring, v and V be the velocities of m and M respectively, when the spring released.
According to the law of conservation of momentum and energy
Question 5
4 / -1

A plane electromagnetic wave of angular frequency ω propagates in a poorly conducting medium of conductivity σ and relative permittivity ε. Find the ratio of conduction current density and displacement current density in the medium.

A

B

C

D

Solution
Question 6
4 / -1

A uniform electric field of magnitude 245 V/m is directed in the negative y direction as shown in figure. The coordinates of point P and Q are (- 0.5m, - 0.8m) and (0.3m, 0.7m) respectively. Calculate the potential difference V_Q - V_P along the path shown in the figure,

A
0

B
245 V

C
321 V

D
367.5 V

Solution

Potential difference between points P and Q is
Question 7
4 / -1

A cylinder of radius r = 1 m and height 3 m filled with a liquid upto 2 m high and is rotated about its vertical axis as shown in the Figure.
The speed of rotation of the cylinder when the point at the centre of the base is just exposed is

A

B

C

D

Solution
Question 8
4 / -1

A charge particle q of mass m₀ is projected along the y-axis at t = 0 from origin with a velocity V₀. If a uniform electric field E₀ also exists along the x-axis, then the time at which the de-Broglie wavelength of the particle becomes half of the initial value is:

A

B

C

D

Solution

Force on charged particle is =qE₀ in x direction.
At any time t velocity in y direction will be same as at t=0 as there is no force in that direction.
At time t velocity in x direction is given by
v_x =a_xt
v_x =(qE₀/m)t

so speed of particle at time t is-

debroglie wavelength is inversly proportional to speed of particle and given by-
(Where R is a constant)
So for half the wavelength speed should be doubled.
Question 9
4 / -1

The beat frequency produced when the following two waves x₁ = 12 sin (484πt − 7πx) and x₂ = 12 sin (480πt − 7πx) are sounded together is

A
4

B
3

C
2

D
1

Solution
Question 10
4 / -1

An 80 kg man standing on ice throws a 4 kg body horizontally at 6 ms⁻¹. The frictional coefficient between the ice and his feet is 0.02. The distance through which the man slips is (g = 10 ms⁻²)

A
0.225 m

B
2.25 m

C
0.115 m

D
0.20 m

Solution

While throwing the body, velocity gained by the man is