CBSE Class 11 Laws of Motion Worksheet C

Law of Motion MCQ Questions with Answers Class 11 Physics Chapter 5

Question. A simple pendulum of length L and mass (bob) M is oscillating in a plane about a vertical line between angular limits − φ and + φ. For an angular displacement θ (|θ |<φ ), the tension in the string and the velocity of the bob are T and v respectively. The following relations hold good under the above conditions
a. T cosθ = Mg
b. T −Mg cosθ = Mv² / L
c. The magnitude of the tangential acceleration of the bob ╿a_T╿ = g sin θ
d. T = Mg cosθ
Answer : B, C

Question. A reference frame attached to the earth:
a. is an inertial frame by definition
b. cannot be an inertial frame because the earth is revolving round the sun
c. is an inertial frame because Newton’s laws are applicable in this frame
d. cannot be an inertial frame because the earth is rotating about its own axis
Answer : B, D

Question. A point mass of 1 kg collides elastically with a stationary point mass of 5 kg. After their collision, the 1 kg mass reverses its direction and moves with a speed of 2 ms^–1. Which of the following statement(s) is/are correct for the system of these two masses?

a. Total momentum of the system is 3 kg-ms^–1
b. Momentum of 5 kg mass after collision is 4 kg-ms^–1
c. Kinetic energy of the centre of mass is 0.75 J
d. Total kinetic energy of the system is 4 J
Answer : A, C

Question. Which of the following are correct?
a. The mechanical advantage for system of pulley is 4. The force needed to lift a mass of 100 kg will be 25 kg-wt
b. A wide hose pipe is held horizontally by a fireman. It deliver water through a nozzle at one litre per second. On increasing the pressure, this increase to tow litre per second. The fireman has now to push forward four times as hard
c. A jet of water with a cross-sectional area A is striking against a wall at an angle θ to the horizontal and rebounds elastically. If the velocity of water jet is υ and the density
ρ, then the normal force acting on the wall is 2Aυ₂ρ cos θ:
d. All of these
Answer : ALL

Question. Refer to the figure, the pulleys and the string are light. T is the tension in the string. Takes g = 10 ms^–2. Which of the following are correct?

a. The acceleration of the system is 5 ms^–2
b. The acceleration of the system is 10 ms^–2
c. T = 0 N
d. T = 5 N
Answer : A, D

Question. If a particle under the action of force F has potential energy U, then in equilibrium:
a. F = 0 but U = 0
b. F ≠ 0 but U = 0
c. F = 0 but U ≠ 0
d. F ≠ 0 but U ≠ 0
Answer : A, C

Question. A body will not be in equilibrium if:
a. Σ F = 0 and Στ = 0
b. Σ F ≠ 0 but Στ = 0 
c. Σ F = 0  but Στ ≠ 0 
d. Σ F ≠ 0  but Στ ≠ 0 
Answer : B, C, D

Question. The equilibrium of a negative point charge between two collinear positive charges:
a. can be stable
b. can be unstable
c. I neutral
d. is not possible
Answer : A, B

Question. If a dipole I situated in a non-uniform field:
a. Σ F = 0 and Στ = 0 
b. Σ F ≠ 0 and Στ = 0 
c. Σ F = 0 but Στ ≠ 0 
d. Σ F ≠ 0 but Στ ≠ 0 
Answer : B, D

Question. A metal sphere is hung by a string fixed on a wall. The forces acting on the sphere are shown in the figure. Which of the following statement is correct?

a. R + T + W = 0
b. T² + R² + W²
c. T = R + W
d. R = W tan θ
Answer : A, B, D

Question. A rocket in a gravity free space burns fuel at a constant rate until time 't0' when all the fuel is burnt out. Initially, the fuel form a substantial portion of the mass of the rocket and the velocity of the rocket is zero. Which of the following graph represents the velocity υ and acceleration a against time ‘t’ for the rocket?

Answer : B, D

Question. A block is resting over a smooth horizontal plane. A constant horizontal force starts acting on it at t = 0. Which of the following graphs are correct?

Answer : B, D

Question. A long block A is at rest on a smooth horizontal surface. A small block B, whose mass if half of A is placed on A at one end and projected along A with some velocity v. The coefficient of friction between the blocks is .μ Then:

a. the blocks will reach a final common velocity v / 3
b. the work done against friction is two-thirds of the initial kinetic energy of B
c. before the blocks reach a common velocity, the acceleration of A relative to B is (2/3)μ g
d. before the blocks reach a common velocity, the acceleration of A relative to B is (3/2)μg
Answer : A, B, C

Question. Two blocks having masses m₁ and m₂ are connected by a thread and are placed on an inclined plane with thread loose as showing in figure.

When the blocks are released:
a. thread will remain loose if m1 < m₂
b. thread will remain loose if plane is smooth
c. thread will remain loose if m₁ is smooth and m₂ is rough
d. thread will remain loose if m₁
is rough and m² is smooth
Answer : B, D

Question. Two men of unequal masses hold on to the two sections of a light rope passing over a smooth light pulley

Which of the following are possible?
a. The lighter man is stationary while the heavier man slides with some acceleration
b. The heavier man is stationary while the lighter man slides with some acceleration
c. The two men slide with the same acceleration in the same direction
d. The two mean slide with the acceleration of the same magnitude in opposite directions
Answer : A, B, D

Question. Figure shows the displacement x of a particle going along the x-axis as a function of time. The force acting on the particle is zero in the regions:

a. AB
b. BC
c. CD
d. DE
Answer : A, C

Match the Column

Question. Match the type of forces in Column I with the statement is Column II.
      Column I                          Column II
(A) Weight of body     1. Force opposite to the force applied to press a body on due to gravity
(B) Thrust                   2. Force due to gravity
(C) Reaction               3. Force acting opposite to weight of body
(D) Friction                 4. Force along the surface in contact
a. A → 2, B → 3, C → 1, D → 4
b. A → 1, B → 2, C → 3, D → 4
c. A → 4, B → 3, C → 2, D → 1
d. A → 3, B → 2, C → 1, D → 4
Answer : A

Question. A body of mass m is placed on a rough inclined surface of inclination equal to angle of repose. The match the statements in Column I with those in Column II.

A → 2 B → 4, C → 3, D → 1
b. A → 2, B → 2, C → 3, D → 4
c. A → 4, B → 3, C → 2, D → 1
d. A → 4, B → 1, C → 3, D → 2
Answer : A

Question. Bodies are in equilibrium even when a number of forces are acting on the body. Column I gives some condition in which body is in some different type of equilibrium mentioned in Column II. Match them and give suitable answer:

a. A→3, B→2, C→1
b. A→1, B→3, C→2
c. A→2, B→1, C→3
d. A→1, B→2, C→3
Answer : A

More question-

1. Why is it desired to hold a gun tight to one’s shoulder when it is being fired?

2. Why does a swimmer push the water backwards?

3. Friction is a self adjusting force. Justify.

4. A force is being applied on a body but it causes no acceleration. What possibilities may be considered to explain the observation?

5. Force of 16N and 12N are acting on a mass of 200kg in mutually perpendicular directions. Find the magnitude of the acceleration produced?

6. An elevator weighs 3000kg. What is its acceleration when the in the tension supporting cable is 33000N. Given that g = 9.8m/s².

7. Write two consequences of Newton’s second law of motion?

8. How is centripetal force provided in case of the following?

(i) Motion of planet around the sun,

(ii) Motion of moon around the earth.

(iii) Motion of an electron around the nucleus in an atom.

9. State Newton’s second, law of motion. Express it mathematically and hence obtain a relation between force and acceleration.

10. A railway car of mass 20 tonnes moves with an initial speed of 54km/hr. On applying brakes, a constant negative acceleration of 0.3m/s² is produced.

(i) What is the breaking force acting on the car?

(ii) In what time it will stop? 

(iii) What distance will be covered by the car before if finally stops?  

Click on link below to download CBSE Class 11 Laws of Motion Worksheet C.