Important Laws of Motion Questions and Solutions
FAQs on Laws of Motion Practice Paper for Students
1. What are the three laws of motion?
The three laws of motion describe how objects move and interact with forces. These are:
Newton's First Law (Law of Inertia): An object remains at rest or in uniform motion unless acted upon by an external force.
Newton's Second Law (Law of Acceleration): The acceleration of an object depends on the net force acting on it and its mass (F = ma).
Newton's Third Law (Action-Reaction Law): For every action, there is an equal and opposite reaction.
- Inertia, force, and reaction are core concepts.
- These laws are fundamental in physics, particularly in the CBSE Class 9/10 Science syllabus.
- Understanding these laws helps in solving real-world problems related to motion and forces.
2. State Newton's first law of motion with examples.
Newton's first law of motion states that an object will remain at rest or in uniform motion in a straight line unless acted upon by an external force. For example:
- A book lying on a table will stay at rest unless you push it.
- A moving car will continue to move unless brakes are applied, which act as an external force.
3. What is the mathematical expression for Newton’s second law of motion?
The mathematical expression for Newton’s second law of motion is F = ma, where:
- F = Force applied (in newtons, N)
- m = Mass of the object (in kilograms, kg)
- a = Acceleration produced (in meters per second squared, m/s2)
4. Explain inertia with an example.
Inertia is the tendency of an object to resist any change in its state of motion or rest. For example:
- A passenger falls forward when a bus stops suddenly due to inertia of motion.
- A coin remains at rest on a card even when the card is swiftly removed.
5. What is momentum? State the law of conservation of momentum.
Momentum is the product of an object’s mass and velocity (p = mv). The law of conservation of momentum states that if no external force acts on a system, the total momentum remains constant.
- This applies in collisions and explosions.
- It is an examinable topic in CBSE.
6. Differentiate between balanced and unbalanced forces.
Balanced forces do not cause a change in the state of rest or motion, while unbalanced forces produce a change in motion. Key differences:
- Balanced: No change in motion, net force is zero.
- Unbalanced: Change in motion, net force is non-zero.
7. What is Newton's third law of motion? Give two examples.
Newton’s third law states: For every action, there is an equal and opposite reaction. Examples include:
- When you jump, your feet push the ground backward; the ground pushes you forward.
- A rocket launches because exhaust gases are pushed downwards, so the rocket moves upwards.
8. Why do athletes often run some distance before taking a long jump?
Athletes run before a long jump to gain momentum, which helps them jump farther.
- Running increases their velocity, thus raising their momentum (p = mv).
- Greater momentum at take-off means greater distance covered.
9. How does friction affect the motion of an object?
Friction opposes the relative motion between two surfaces in contact, causing objects to slow down and eventually stop. Important points:
- Friction acts opposite to the direction of motion.
- It is necessary for walking but also leads to energy loss as heat.
- Reducing friction is useful in machines for efficiency.
10. What is an application of Newton’s laws of motion in daily life?
Newton’s laws of motion are applied in numerous daily activities. For example:
- Seat belts in cars protect passengers by counteracting inertia in case of sudden stops (first law).
- Throwing or catching a ball involves calculation and control of force and acceleration (second law).
- Walking or swimming uses action-reaction pairs (third law).
11. What is the SI unit of force?
The SI unit of force is the Newton (N).
- 1 Newton is the force required to accelerate a mass of 1 kilogram by 1 meter/second2.
- This is fundamental knowledge for physics students.
12. What are the factors affecting friction?
The main factors influencing friction are:
- Nature of the surfaces in contact (smooth or rough)
- The normal force pressing the surfaces together
