# Force and Laws of Motion - Class 9 Ncert Cbse Science Physics - MCQs

## Class IX, FORCE AND LAWS OF MOTION

### Ncert Cbse Science (Physics) Guide

#### Multiple Choice Questions (MCQs)

Question.1: If a bus starts suddenly, the passengers in the bus will tend to fall
(a) In the direction opposite to the direction of motion of bus.
(b) In the same direction as the direction of motion of bus.
(c) Sideways.
(d) None of the above.
Question.2: An athlete runs some distance before taking a long jump because
(a) He gains energy to take him through long distance.
(b) It helps him to apply large force.
(c) By running action and reaction forces increase.
(d) By running the athlete gives himself larger inertia of motion.
Question.3: A rider on a horseback falls back when horse starts running all of a sudden because
(a) Rider is taken back.
(b) Rider is suddenly afraid of falling.
(c) Inertia of rest keeps the upper part of body at rest whereas the lower part of the body moves forward with the horse.
(d) None of the above.
Question.4: Inertia is a property of a body by virtue of which the body is
(a) Unable to change by itself the state of rest.
(b) Unable to change by itself the state of uniform motion in a straight line.
(c) Unable to change by itself the direction of motion.
(d) Unable to change by itself the state of rest or uniform motion in a straight line.
Question.5: Qualitative definition of force is given by
(a) Newton’s first law of motion.
(b) Newton’s second law of motion.
(c) Newton’s third law of motion.
(d) Newton’s law of gravitation.
Question.6: SI unit of force is
(a) kg m/s.
(b) Newton.
(c) Dyne.
(d) None of these.
Question.7: A driver accelerates his car first at the rate of 1.8 m/s2 and then at the rate of 1.2 m/s2. The ratio of the two forces exerted by the engine in the two cases will be
(a) 1: 2
(b) 2: 1
(c) 2: 3
(d) 3: 2
Question.8: Newton’s law of motion gives the measure of
(a) Force
(b) Acceleration
(c) Momentum
(d) Impulse.
Question.9: An object will continue to accelerate until
(a) The resultant force begins to decrease.
(b) The resultant force on it is zero.
(c) The velocity changes direction.
(d) The resultant force on it is increased continuously.
Question.10: A canon after firing recoils due to
(a) Conservation of energy.
(b) Backward thrust of gases.
(c) Newton’s third law of motion.
(d) Newton’s first law of motion.
Question.11: A rocket or jet engine works on the principle of
(a) Conservation of energy
(b) Conservation of momentum
(c) Conservation of mass
(d) Newton’s second law of motion.
Question.12: kg.m/s2 is the unit of
(a) Momentum
(b) Speed
(c) Acceleration
(d) Force
Question.13: Rate of change of momentum is equal to
(a) Acceleration
(b) Work done
(c) Force
(d) Impulse
Question.14: When an object undergoes acceleration
(a) Its speed always increases
(b) Its velocity always increases.
(c) It always falls towards the earth
(d) A force always acts on it.
Question.15: When a net force acts on an object, the object will be accelerated in the direction of the force with acceleration proportional to
(a) The force on the object
(b) The velocity of the object
(c) The mass of the object
(d) The inertia of the object
Question.16: The action and reaction forces referred to in the third law
(a) Must act on the same object.
(b) May act on different objects.
(c) Must act on different objects.
(d) Need not be equal in magnitude but must have the same direction.