In this section we provides Physics Chapter Force Multiple Choice Questions & Answers with solutions for CBSE Class 9.
1. Force is a :
(A) Vector quantity
(B) Scalar quantity
(C) May be scalar or may be vector quantity
(D) None of these
Solution
Sol. Vector
2. A block of mass 4 kg is suspended through two light spring balances A and B. Then A and B will read respectively, in figure
(A) 4 kg and zero kg
(B) zero kg and 4 kg
(C) 4 kg and 4 kg
(D) 2 kg and 2 kg
Solution
Sol. Both will read 4kg
3. A boy sitting on the topmost berth in the compartment of a train which is just going to stop on a railway station, drops an apple aiming at the open hands of his brother situated vertically below his hands at a distance of about 2 m. The apple will fall :
(A) In the hand of his brother
(B) Slightly away from the hands of his brother in the direction of motion of the train
(C) Slightly away from the hands of his brother in the direction opposite to the direction of motion of the train
(D) None of the above
Solution
Sol. Brother with train undergoes retarded horizontal motion but apple undergoes uniform forward motion.
4. Which of the following has largest inertia :
(A) A pin
(B) An ink pot
(C) Your physics book
(D) Your body
Solution
Sol. Inertia mass
5. The law which defines force is :
(A) Newton’s third law
(B) Newton’s first law
(C) Newton’s second law
(D) None of these
Solution
Sol. First Law
6. A man sitting in a train in motion is facing the engine. He tosses a coin up, the coin falls behind him. The train is moving :
(A) forward with uniform speed
(B) backward with uniform speed
(C) forward with acceleration
(D) forward with deceleration
Solution
Sol. Man with train, and coin uniform horizontal motion so train is accelerating.
7. An Athlete runs over a certain distance before taking a long jump, because due to this :
(A) His mass gets decreases, so he can jump over a long distance
(B) He gains inertia of motion so he can take a longer jump
(C) He gets the power of god so he can take a longer jump
(D) He follows law of conservation of linear momentum.
Solution
Sol. Less force required.
8. When a bus starts suddenly the passengers standing on it, Lean backwards in the bus. This is an example of :
(A) Newton’s first law
(B) Newton’s second law
(C) Newton’s third law
(D) None of Newton’s law
Solution
Sol. First Law
9. If a body at rest is acted upon by equal and opposite forces :
(A) The resultant would be zero
(B) The body would not move at all
(C) Both A and B are correct
(D) Neither A nor B is correct
Solution
Sol. Balanced Forces
10. If the momentum of a body increases by 0.01%, its kinetic energy will increase by
(A) 0.01 %
(B) 0.02%
(C) 0.04%
(D) 0.08%
Solution
Sol. KE = \frac{{{p^2}}}{{2m}}\,\, \Rightarrow \,\,\,KE = 2(\% \,p) = 0.02\,\%
11. A long – jumper runs before jumping because :
(A) He covers a greater distance
(B) He maintains momentum conservation
(C) He gains energy by running
(D) He gains momentum
Solution
Sol. F = \frac{{\Delta p}}{t} = \Delta p \downarrow \Rightarrow F \downarrow
12. Which of the following statements is/are incorrect
(1) While we are sitting one chair no force is acting on us.
(2) Without force of friction it is possible to walk on a surface
(3) All contact forces are normal forces.
(4) Force of friction, if acting may not be parallel to the two surface in contact
(A) Only 1 and 2
(B) Only 2, 3 and 4
(C) Only 1, 3 and 4
(D) All are incorrect
Solution
Sol. All
13. A force produces an acceleration of 0.5 m/s2 in a body of mass 3.0 kg. If same force acts an a body of mass 1.5 kg, the acceleration produced in it is:
(A) 3.0 m m/s2
(B) 1.0 m/s2
(C) 5.0 m/s2
(D) 7 m/s2
Solution
Sol. a = \frac{{0.5 \times 3}}{{1.5}} = 1\,{\text{m/}}{{\text{s}}^{\text{2}}}
14. A ball of mass m strikes the bat with a speed v & goes back in the opposite direction with speed 2v. If ball was in contact for t time then force applied by the bat is :
(A) \frac{{mv}}{t}Â
(B) \frac{{3mv}}{t}Â
(C) \frac{{2mv}}{t}Â
(D) mvt
Solution
Sol. F = \frac{{m(V + 2V)}}{t} = \frac{{3mV}}{t}
15. A ball of mass 100 gm moving with a velocity of 10m/sec is being hit by a bat, it starts moving with 10 m/s in opposite direction. The force on the ball by the bat acts for 0.01 sec. The average force exerted on the ball by the bat is :
(A) 100 N
(B) 200 N
(C) 300 N
(D) 400 N
Solution
Sol. \frac{{100}}{{1000}}\left( {\frac{{20}}{{0.01}}} \right) = 200N
16. 
The reading of spring balance will be :
(A) 100 N
(B) 200 N
(C) 300 N
(D) 400 N
Solution
Sol. 100N
17. In the following diagram, acceleration of the body would be :
(A) 0
(B) 0.4 m/s2
(C) 4 m/s2
(D) 2 m/s2
Solution
Sol. a = \frac{{7 - 5}}{5} = 0.4
18. Force acting on a body :
(A) Must increase its momentum
(B) Must decrease its momentum
(C) May decrease or increase its momentum
(D) None of these
Solution
Sol. Decrease/Increase
19. A body of mass 10 kg is moving with kinetic energy of 2000J. The momentum of body is :
(A) 20 kg.m/s
(B) 200 kg m/s
(C) 2000 kg. m/s
(D) 400 kg.m/s
Solution
Sol. P = \sqrt {2 \times 10 \times 2000} = 200 kg × m/s
20. A machin gun fires a bullet of mass 40 g with velocity 1200 ms–1. The person holding it can apply a maximum force of 144 newton on the gun. What is the maximum number of bullets that can be fired per second.
(A) 3
(B) 4
(C) 5
(D) 7
SolutionAns. (A)
Sol. n \times \frac{{40}}{{1000}} \times 1200 \leqslant 144\,\, \Rightarrow \,\,n \leqslant 3
21. An object of mass 2 kg. is moving with a velocity of 3 m/s and collides head on with an object of mass 1 kg. moving in the opposite direction with a velocity of 4 m/s. After collision , both objects stick so that they move with a common velocity v equal to :
(A) \frac{2}{3}{\text{m/s}}
(B) 1 m/s
(C) 2 m/s
(D) 3 m/s
Solution
Sol. (2)(3) + (1) (–4) = (2 + 1) (v)
V = \frac{2}{3}\,{\text{m/s}}
22. When a bullet is fired from a gun. The gun recoils to :
(A) Conserve mass
(B) Conserve momentum
(C) Conserve K.E
(D) None of these
Solution
Sol. Momentum conserved
23. Action and reaction :
(A) Acts on some body
(B) Acts on different bodies
(C) Any of A & B
(D) Can’t say
Solution
Sol. On Different Bodies
24. A bullet in motion hits and gets embedded in a solid resting on a frictionless table. What is conserved :
(A) Momentum and K.E.
(B) Momentum alone
(C) K.E. alone
(D) None of these
Solution
Sol. Momentum
25. A rocket works on the :
(A) First law of motion
(B) Second law of motion
(C) Third law of motion
(D) Law of conservation of energy
Solution
Sol. 3rd law
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