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MCQ & Solution - Force and Laws of Motion | Science Class 9 PDF Download

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.
Answer: a
 
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.
Answer: d
 
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.
Answer: c
 
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.
Answer: d
 
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.
Answer: a
 
Question.6: SI unit of force is  
(a) kg m/s.
(b) Newton.
(c) Dyne.
(d) None of these.
Answer: b
 
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
Answer: d
 
Question.8: Newton’s law of motion gives the measure of
(a) Force
(b) Acceleration
(c) Momentum
(d) Impulse.
Answer: a
 
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.
Answer: b
 
Question.10: A cannon 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.
Answer: c
 
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.
Answer: b
 
Question.12: kg.m/s2 is the unit of
(a) Momentum
(b) Speed
(c) Acceleration
(d) Force
Answer: d
 
Question.13: Rate of change of momentum is equal to
(a) Acceleration
(b) Work was done
(c) Force
(d) Impulse
Answer: c
 
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.
Answer: d
 
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
Answer: a
 
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.
Answer: c
The document MCQ & Solution - Force and Laws of Motion | Science Class 9 is a part of the Class 9 Course Science Class 9.
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FAQs on MCQ & Solution - Force and Laws of Motion - Science Class 9

1. What are the three laws of motion?
Ans. The three laws of motion were first introduced by Sir Isaac Newton. They are - 1. An object at rest will remain at rest, and an object in motion will remain in motion at a constant velocity unless acted upon by an external force. This is known as the law of inertia. 2. The acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass. This is known as the law of force and acceleration. 3. For every action, there is an equal and opposite reaction. This is known as the law of action-reaction.
2. What is the formula for force?
Ans. The formula for force is given by - Force = mass x acceleration, where mass is measured in kilograms (kg) and acceleration is measured in meters per second squared (m/s²). The unit of force is Newton (N).
3. What is the difference between weight and mass?
Ans. Mass and weight are two different physical quantities. Mass is the amount of matter present in an object, whereas weight is the force exerted by gravity on the object. Mass is a scalar quantity and is measured in kilograms (kg), whereas weight is a vector quantity and is measured in Newtons (N). Mass remains constant everywhere, but weight changes with the change in the gravitational field.
4. What is Newton's first law of motion?
Ans. Newton's first law of motion states that an object at rest will remain at rest, and an object in motion will remain in motion at a constant velocity unless acted upon by an external force. This is known as the law of inertia. In other words, an object will continue to do what it is doing until something else acts on it to change its state of motion.
5. What is the importance of Newton's laws of motion in our daily lives?
Ans. Newton's laws of motion have a significant impact on our daily lives. For example, they explain why we wear seat belts while driving, why a ball thrown in the air eventually falls back down, why we feel a force pushing us back when a vehicle accelerates rapidly, and many more. These laws are used in designing vehicles, machines, and structures to ensure their safety and efficiency. They are also crucial in the field of space travel and exploration.
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