CBSE Class 9 Science Force and Laws of Motion MCQs Set A

Question: In the following example, try to identify the number of times the velocity of ball changes - A football player kicks a football to another player of his team who kicks the football towards the goal. The goalkeeper of the opposite team collects the football and kicks it towards a player of his own team.
(a) Five times
(b) Three times
(c) Four times
(d) Six times

Answer : B

Question: There will be a change in the speed or in the direction of motion of a body when it is acted upon by
(a) An Unbalanced force
(b) Balanced Force
(c) Uniform force
(d) Zero Force

Answer : A

Question: A hammer of mass 500 g, moving at 50m/s, strikes a nail. The nail stops the hammer in a very short time of 0.01 s. The force of the nail on the hammer is
(a) 3500N
(b) 1000N
(c) 2500N
(d) 500N

Answer : C

Question: The action and reaction forces referred to in the third law
(a) Must act on different objects
(b) Must act on the same objec
(c) May act on different objects
(d) Need not be equal in magnitude but act in the same direction

Answer : A

Question: An object will continue to accelerate until the
(a) Resultant force begins to decrease
(b) The velocity changes direction
(c) Resultant force on it is increased continuously
(d) Resultant force on it is zero

Answer : D

Question: Qualitative definition of Force is given by
(a) Newtons first law of motion
(b) Newtons Second law of motion
(c) Newtons third law of motion
(d) Newtons law of gravitation

Answer : A

Question: The object shown below moves with constant velocity. Two forces are acting on the object. Considering negligible friction , the resultant force will be 

(a) 17 N leftwards
(b) 7N rightwards
(c) 3 N leftwards
(d) 10 N leftwards

Answer :  C

Question: Type of inertia that tends to resist the change in case of an -Athlete often jumps before taking a long jump
(a) Inertia of motion
(b) Inertia of rest
(c) Inertia of direction
(d) Uniformly accelerated motion

Answer : A

Question: A passenger in a moving train tosses a coin which falls
(a) Behind him
(b) In front of him
(c) Falls outside the train
(d) Will not move

Answer : A

Question: A bullet of mass 20gm is fired from a gun of mass 8kg with a velocity of 400 m/s, calculate the recoil velocity of gun
(a) -2m/s
(b) 1m/s
(c) 2m/s
(d) -1m/s

Answer : D

Question: Rocket works on the principle of conservation of
(a) Energy
(b) Mass
(c) momentum 
(d) velocity

Answer : C

Question: An object of mass 2 kg is sliding with a constant velocity of 4 m/ s on a frictionless horizontal table. The force required to keep the object moving with the same velocity is
(a) 8N
(b) 2N
(c) 32N
(d) 0 N 

Answer : D

Question: Inertia is a measure of
(a) Mass
(b) velocity
(c) Force
(d) acceleration

Answer : A

Question: Formula to find the Force is
(a) F= ma
(b) F= m/a
(c) F= a/m
(d) a=Fm

Answer : A

Question: Force required in accelerating a 2 kg mass at 5 m/s2 and a 4 kg mass at 2 m/s2
(a) 2kg mass at 5m/s2 is less than 4 kg mass at 2 m/s2
(b) Same in both the cases
(c) 2kg mass at 5m/s2 is greater than 4 kg mass at 2 m/s2
(d) Zero in both the cases

Answer : C

Question.. 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.

Answer :   A

Question. Which of the following is the unit of linear momentum?
(a)  kg m/s
(b) kg ms
(c) kgms−2
(d) kg

Answer :   B

Question. A plate, a ball and a child all have the same mass. The one having more inertia is the
(a) plate
(b) ball
(c) child
(d) All have equal inertia

Answer :   D

Question. 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.

Answer :   D

Question. A goalkeeper in a game of football pulls his hands backwards after holding the ball shot at the goal. This enables the goalkeeper to:
(a) Exert large force on the ball
(b) Increases the force exerted by the ball on hands
(c) Increase the rate of change of momentum
(d) Decrease the rate of change of momentum

Answer :   D

Question. The acceleration of an object is
(a) inversely proportional to its mass
(b) directly proportional to the applied force
(c) resisted by inertia
(d) all of the above

Answer :   D

Question.: 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.

Answer :   B

Question. The S.I. unit of force is
(a) Newton-metre
(b) Newton
(c) Newton per second
(d) Newton per square metre

Answer :   B

Question.. Rate of change of momentum is equal to
(a) Acceleration
(b) Work done
(c) Force
(d) Impulse

Answer :   C

Question. 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.

Answer :   C

Question. If an object moves with a uniform velocity we can conclude that
(a) there is no force acting on the body
(b) no unbalanced force acts on it
(c) an unbalanced force acts on the body
(d) it has uniform acceleration

Answer :   B

Question. When a force is exerted on an object, it can change its:
(a) State
(b) Position
(c) Shape
(d) All the above

Answer :   D

Question . Rocket works on the principle of conservation of
(a) velocity
(b) Mass
(c) Linear Momentum
(d) Energy

Answer :   C

Question. The seat belts are provided in the cars so that if the car stops suddenly due to an emergency braking, the persons sitting on the front seats are not thrown forward violently and saved from getting injured. Can you guess the law due to which a person falls in forward direction on the sudden stopping of the car?
(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

Answer :   A

Question. Two equal masses m each moving in the opposite direction with the same speed v collide and stick to each other. The velocity of the combined mass is
(a) v
(b) 2v
(c) v/2
(d) zero

Answer :   D

Question. When unbalanced forces act on a body, the body:
(a) Must move with uniform velocity
(b) Must remain at rest
(c) Must experience acceleration
(d) Must move in a curved path

Answer :   C

Question. A passenger in a moving train tosses a coin which falls behind him. Observing this statement what can you say about the motion of the train?
(a) Accelerated
(b) Retarded
(c) Along circular tracks
(d) Uniform

Answer :   A

Question. An object of mass 20 kg is moving with a velocity of 10 m/s. Its momentum will be:
(a) 2000 kg.m/s
(b) 20 kg.m/s
(c) 2 kg.m/s
(d) 200 kg.m/s

Answer :   D

Question. When a 12 N force acts on 3 kg mass for a second, the change in velocity is (in m/s)
(a) 36
(b) 4
(c) 2
(d) 18

Answer :   B

Question. The acceleration of an object is
(a) inversely proportional to its mass
(b) directly proportional to the applied force
(c) resisted by inertia
(d) all of the above

Answer :   D