Worksheet: Force and Laws of Motion

# Worksheet: Force and Laws of Motion - Science Class 9

Q.1. Fill in the blanks
(i) When a running car stops suddenly, the passengers are jerked ___________.
(ii) In collisions and explosions, the total _________ remains constant, provided that no external ___________ acts.
(iii) If there were no unbalanced force of ___________ and no _________ resistance, a moving bicycle would go on moving for ever.
(iv) When a stationary car starts suddenly, the passengers are jerked ___________.
(v) To every action, there is an ___________ and __________ reaction.

Q.2. The inability of the body to change its state of rest or motion is :-
(a) Momentum
(b) Force
(c) Inertia
(d) Acceleration.

Q.3. The S.I. unit of weight is:
(a) Newton
(b) Newton m
(c) Newton/sec
(d) Newton m/s

Q.4. A batsman hits a cricket ball which then rolls on a level ground. After covering a short distance, the ball comes to rest. The ball slows to a stop because
(a) the batsman did not hit the ball hard enough.
(b) velocity is proportional to the force exerted on the ball.
(c) there is a force on the ball opposing the motion.
(d) there is no unbalanced force on the ball, so the ball would want to come to rest.

Q.5. If the initial velocity is zero then the force acting is :-
(a) Retarding
(b) Acceleration
(c) Both
(d) None.

Q.6. An object experiences a net zero external unbalanced force. Is it possible for the object to be travelling with a non-zero velocity? If yes, state the conditions that must be placed on the magnitude and direction of the velocity. If no, provide a reason.

Q.7. Why do you fall in the forward direction when a moving bus brakes to a stop and fall backwards when it accelerates from rest?

Q.8. Why is the weight of the object more at the poles than at the equator?

Q.9. Explain why some of the leaves may get detached from a tree if we vigorously shake its branch.

Q.10. Why is it advised to tie any luggage kept on the roof of a bus with a rope?

Q.11. Why does the passenger sitting in a moving bus are pushed in the forward direction when the bus stops suddenly?

Q.12. State Newton’s first law of Motion?

Q.13. Define force and what are the various types of forces?

Q.14. State Newton’s second law of motion?

Q.15. When a carpet is beaten with a stick, dust comes out of it. Explain.

The document Worksheet: Force and Laws of Motion | Science Class 9 is a part of the Class 9 Course Science Class 9.
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## Science Class 9

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## FAQs on Worksheet: Force and Laws of Motion - Science Class 9

 1. What are the three laws of motion? Ans. The three laws of motion are: 1. Newton's First Law: An object will remain at rest or continue to move in a straight line at a constant speed unless acted upon by an external force. 2. Newton's Second Law: The force acting on an object is equal to the mass of the object multiplied by its acceleration (F = ma). 3. Newton's Third Law: For every action, there is an equal and opposite reaction.
 2. How does force affect the motion of an object? Ans. Force can change the motion of an object. If a force is applied to an object, it can either make the object start moving, stop moving, or change its direction or speed. The acceleration produced by a force depends on the mass of the object. The greater the force applied or the smaller the mass of the object, the greater the acceleration.
 3. What is inertia? Ans. Inertia is the tendency of an object to resist any change in its state of motion. It is related to Newton's First Law of Motion. Objects with more mass have greater inertia, meaning they are more resistant to changes in their motion. Conversely, objects with less mass have less inertia and are easier to move or change their motion.
 4. What is the relationship between mass and acceleration? Ans. According to Newton's Second Law of Motion, the acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass. This relationship can be expressed mathematically as: a = F/m, where a is acceleration, F is the net force, and m is the mass of the object. Therefore, if the mass of an object increases, its acceleration decreases for a given force, and vice versa.
 5. How does Newton's Third Law of Motion apply to real-life situations? Ans. Newton's Third Law states that for every action, there is an equal and opposite reaction. This law can be observed in various real-life situations. For example, when you push a wall, the wall pushes back with an equal force, preventing you from moving it. Similarly, when a person jumps off a boat, the boat moves backward due to the force exerted by the person. This law also explains how rockets work by expelling gases in one direction to generate a force in the opposite direction, propelling the rocket forward.

## Science Class 9

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