Physics Model Question Paper 15: (For Class 11 and 12 and Pre-Medical/Engineering Entrance)

1.

A particle of charge e and mass m moves with a velocity u in a magnetic filed B applied perpendicular to the motion of the particle. The radius r of its path in the field is ______.

(A)

(B)

(C)

(D)

Answer: (D)

2.

A particle of mass m is located in a one dimensional potential field where potential energy is given by:

V(x) = A(1 – cos px), where A and p are constants. The period of small oscillations of the particle is

(A)

(B)

(C)

(D)

Answer: (B)

3.

A particle of mass m₁ moves with velocity v₁ and collides with another particle at rest of equal mass. The velocity of the second particle after the elastic collision is

(A) 2v₁

(B) v₁

(C) -v₁

(D) 0

Answer: (B)

4.

A perfect gas at 27°C is heated at constant pressure so as to double its volume. The increase in temperature of the gas will be ______.

(A) 300°C

(B) 54°C

(C) 327°C

(D) 600°C

Answer: (A)

5.

A person of mass 60 kg is inside a lift of mass 940 kg and presses the button one control panel. The lift starts moving upwards with an acceleration 1.0 m/s². If g = 10 ms^–2, the tension in the supporting cable is

(A) 1200 N

(B) 8600 N

(C) 9680 N

(D) 11000 N

Answer: (D)

6.

A plane progressive wave is given by y = 2 cos 6.284 (330 t – x). What is period of the wave?

(A)

(B) 2p ´ 330 S

(C) (2p ´ 330)^-1S

(D)

Answer: (A)

7.

A plano-concave lens is made of glass of refractive index 1.5 and the radius of curvature of its curved face is 100 cm. What is the power of the lens?

(A) + 0.5 D

(B) – 0.5 D

(C) – 2 D

(D) + 2 D

Answer: (B)

8.

A planoconvex lens has a maximum thickness of 6 cm. When placed on a horizontal table with the curved surface in contact with the table surface, the apparent depth of the bottommost point of the lens is found to be 4 cm. If the lens is inverted such that the plane face of the lens is in contact with the surface of the table, the apparent depth of the center of the plane face is found to be cm. The radius of curvature of the lens is ______.

(A) 34 cm

(B) 128 cm

(C) 75 cm

(D) 68 cm

Answer: (A)

9.

A prism having refractive index 1.414 and refracting angle 30° has one of the refracting surfaces silvered. A beam of light incident on the other refracting surface will retrace its path, if the angle of incidence is ______.

(A) 45°

(B) 60°

(C) 30°

(D) 0°

Answer: (A)

10.

A prism of a certain angle deviates the red and blue rays by 8° and 12° respectively. Another prism of the same angle deviates the red and blue rays by 10° and 14° respectively. The prisms are small angled and made of different materials. The dispersive powers of the materials of the prisms are in the ratio

(A) 11 : 9

(B) 6 : 5

(C) 9 : 11

(D) 5 : 6

Answer: (B)

11.

A proton and a deuteron with the same initial kinetic energy enter a magnetic field in a direction perpendicular to the direction of the field. The ratio of the radii of the circular trajectories described by them is

(A) 1 : 2

(B) 1 : 1

(C) 1 :

(D) 1 : 4

Answer: (C)

12.

A proton travelling at 23° w.r.t. the direction of a magnetic field of a strength 2.6 mT experiences, a magnetic force of 6.5 ´ 10^–17 N. What is the speed of the proton?

(A) 2 ´ 10⁵ m/second

(B) 4 ´ 10⁵ m/second

(C) 6 ´ 10⁵ m/second

(D) 8 ´ 10⁵ m/second

Answer: (B)

13.

A radio active element forms its own isotope after 3 consecutive disintegrations. The particles emitted are

(A) 2a particles and Ib particle

(B) 2b particles and 1g particle

(C) 2b particles and 1a particle

(D) 3b particles

Answer: (C)

14.

A radio active substance contains 10,000 nuclei and its half life period is 20 days. The number of nuclei present at the end of 10 days is

(A) 7,500

(B) 8,000

(C) 9,000

(D) 7,070

Answer: (D)

15.

A radioactive nucleus of mass number A, initially at rest, emits an a-particle with a speed v. The recoil speed of the daughter nucleus will be

(A)

(B)

(C)

(D)

Answer: (C)