# JEE Main Physics Important Questions with Answers

(Q.Nos 1-12) : Have one or more than one correct option. You will be awarded 3 marks for correct answer and –1 mark (minus one mark)for wrong answer.
(Q.Nos 13-16) : These Questions are Assertion & Reasoning , with only one correct option.You will be awarded 3 marks for correct
answer and –1 marks for wrong answer.
(Q.Nos 17-22): These Questions are Comprehension, with only one correct option. You will be awarded 3 marks for correct answer
and –1 marks for wrong answer.

1. A block is held against a rough wall by applying a horizontal force on the block perpendicular to the wall. If another horizontal
force is also applied on the block but along the wall, the frictional force on the block by the wall is
A) along the wall and horizontal
B) along the wall and vertical
C) along the wall and inclined to the horizontal
D) cannot be decided as the value of the forces applied are not given.

2. A particle of mass m is moving in a circular path of constant radius r such that its centripetal acceleration is varying in magnitude with time t.
A) the net acceleration of the particle is constant in magnitude but varying in direction.
B) the net acceleration of the particle is varying in magnitude but has a constant direction.
C) the net acceleration of the particle is neither constant in magnitude nor in direction.
D) none of the above can be decided as the variation in the magnitude of the centripetal acceleration with time is
not given.

3. When a block is suspended from a spring balance A the balance reads 2 N. Another balance B reads 5 N when a beaker with some liquid is put on the pan of the balance. The two balances are now so arranged that the hanging mass is inside the liquid in the beaker without touching the bottom of the beaker. In this situation
A) balance A reads less than 2 N.
B) balance B reads more than 5 N
C) if the spring of balance A is cut and the block is allowed to settle down in the liquid on the bottom of the beaker then the
reading of the balance B will be 7 N
D) none of the above

4. A cylinder rolls up an inclined plane, reaches some height and then rolls down the plane without slipping throughout these motions.
The work done by the frictional force
A) in translating the cylinder up the plane is zero
B) in rotating the cylinder up the plane is zero
C) is zero in totally translating plus rotating during the upward journey and translating plus rotating during the downward journey
separately.
D) is zero in totally translating plus rotating during the upward and downward journey combined.

5. Whenever two spherical bodies collide in mid air
A) their momentum cannot be conserved in the vertical direction as gravitational force is acting on them.
B) their momentum can be conserved in any direction.
C) their momentum can be conserved along their common tangent only.
D) their momentum cannot be conserved along their common normal

6. Water is flowing in stream line motion through a tube with its axis horizontal. Consider two points A and B in the tube at the same horizontal level
A) the pressures at A and B are equal for any shape of the tube.
B) the pressures are never equal
C) the pressures are equal if the tube has a uniform cross section
D) the pressures may be equal even if the tube has a non uniform cross section.

7. If two soap bubbles of different radii are connected by a tube,
A) air flows from bigger bubble to smaller bubble till the sizes
become equal
B) air flows from bigger bubble to smaller bubble till the sizes are interchanged.
C) air flows from smaller bubble to bigger bubble.
D) the air does not flow at all as the pressure of air in both the bubbles is already equal

8. When two wave pulses approach each other and are identical in shape except that one is inverted with respect to the other,
A) at one instant the displacement of all the particles will be zero.
B) at one instant when the displacement of all the particles is zero, the kinetic energy of all the particles at that instant is also
zero.
C) at no instance the displacement of all the particles will be zero.
D) at one instant when the displacement of all the particles is zero, the kinetic energy of all the particles at that instant is not
zero.

9. A cylindrical resonance tube open at both the ends has a fundamental frequency f in air. Half of the length of the tube is dipped vertically in water. The fundamental frequency of the air column now is
A) 2f B) f / 2 C) f D) f / 3

10. Consider the following two statements:
A: the internal energy of a thermodynamic system necessarily increases if heat is added to it.
B: the internal energy of a thermodynamic system necessarily increases if the temperature of the system is increased.
A) A is correct, B is wrong
B) A is wrong, B is correct
C) both A and B are wrong
D) both A and B are correct

11. When we place a gas cylinder on a van and the van moves,
A) the kinetic energy of the molecules increases
B) the temperature of the gas increases C) neither the temperature
of the gas nor the kinetic energy of the molecules increases
D) the temperature of the gas does not increase.

12. A piece of charcoal and a piece of shining steel of the same area are kept for a long time in an open lawn in bright sun.
A) the purpose of mentioning that both of them have been kept in the lawn for a long time is to conclude that the temperatures of both of them have become same.
B) steel will have absorbed more heat than the charcoal
C) if both are picked up by bare hands, steel will be felt hotter than the charcoal because it is better conductor
D) if the two are picked from the lawn and placed in a cold chamber,
steel will lose heat at a faster rate than the charcoal as steel is
a better conductor.

ASSERTION AND REASON TYPE:
Bubble (A) if both the statements are TRUE and ST–2 is the correct
explanation of ST– 1
Bubble(B) if both the statements are TRUE but ST–2 is NOT the correct explanation of ST-1
Bubble (C ) if STATEMENT –1 is TRUE and STATEMENT –2 is FALSE
Bubble (D ) if STATEMENT –1 is FALSE and STATEMENT –2 is TRUE.

13. Statement 1: The energy density in dielectrics is greater than that in vacuum for the same electric field.
Statement 2: Inside the dielectrics placed in an external electric field there is a dipole moment that appears in the volume. The
dipole moments interact with each other so as to give this additional energy.

14. Statement 1: There is a uniform magnetic field in a cubicle region and is zero outside. We can project a charged particle from outside into the field so that the particle describes a complete circle in the field.
Statement 2: The net charge in a current carrying wire is zero. Still a magnetic field exerts a force on it.

15. Statement 1: When a paramagnetic substance is placed in a magnetic field, the field in the substance is more than the applied field.
Statement 2: when a dielectric is placed in an electric field, it gets polarized and the electric field in the polarized material is less than the applied field.

16. Statement 1: electrons in a conductor have no motion in the absence of a potential difference.
Statement 2: electrons in a conductor have no systematic motion in the absence of a potential difference.
Comprehension I: The convex surface of a thin concavo-co vex lens of glass of refractive index 1.5 has a radius of curvature 20 cm. The concave surface has a radius of curvature 60 cm. The convex side is
silvered and placed on a horizontal surface.

17. The position where a pin should be placed on the optic axis such that its image is formed at the same place is
A) 20 cm B) 60 cm C) 15 cm D) not possible

18. If the concave part is filled with water of refractive index 4/3 and the image of the pin placed on the optic axis should still coincide with the position of the pin then
A) the pin needs to be shifted closer to the lens than where it was before water was filled
B) the pin needs to be shifted away from the lens than where it was before water was filled.
C) the image of the pin cannot coincide with the position of the pin after water is filled.
D) the pin should be placed where it was before filling the water to have its image coincide with it.

19. The position of the pin on the optic axis after the concave part is filled with water such that its image is formed at the same place is
A) 1.16 cm B) 13.84 cm C) 15 cm D) not possible.

Comprehension 2: The figure shows two identical parallel plate
capacitors connected to a battery with the switch S closed as shown. The switch is now opened and the free space between the plates of the capacitors is filled with a dielectric of dielectric constant 3.

20. The total electrostatic energy stored in both the capacitors before the dielectric is introduced is
A) 2CV2 B) (1/2) CV2 C) CV2 D) (1/4)CV2

21. The capacitor in which the potential difference remains constant while the dielectric is being introduced is
A) A B) B C) both A and B D) neither A nor B

22. The total electrostatic energy stored in both the capacitors after the dielectric is introduced is
A) (3/2)CV2 B) (1/6)CV2 C) (5/3)CV2 D) zero

KEY:
1) C 2) C 3) A, B, C 4) C 5) B 6) C, D 7) C 8) A, D 9) C 10) B 11) A 12) A, C 13) A 14) D 15) B 16) D 17) C 18) A 19) B 20) C 21) A 22) C.