Laws of Motion 11 Physics — Revision Notes
Newton's laws of motion form the foundation of classical mechanics, explaining how objects move and respond to forces. These laws are fundamental to unders
TL;DR: Newton's laws of motion form the foundation of classical mechanics, explaining how objects move and respond to forces. These laws are fundamental to u…
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Newton's laws of motion form the foundation of classical mechanics, explaining how objects move and respond to forces. These laws are fundamental to unders
Newton's First Law of Motion
- An object at rest remains at rest unless acted upon by a force
- An object in motion continues with constant velocity unless acted upon by a force
- This law describes inertia: resistance to change in motion
- No net force means acceleration is zero
- Objects naturally maintain their state of motion
Newton's Second Law of Motion
- Force equals mass times acceleration: F equals m times a
- Acceleration is directly proportional to net force and inversely proportional to mass
- A larger force produces greater acceleration
- A larger mass requires more force for same acceleration
- Direction of acceleration is same as direction of net force
Newton's Third Law of Motion
- For every action, there is equal and opposite reaction
- Forces always occur in pairs between two objects
- Action and reaction forces act on different objects
- Magnitudes of action and reaction are equal
- Directions of action and reaction are opposite
Applications of Laws of Motion
- Seatbelts work by applying force to stop passenger during sudden deceleration
- Rockets propel forward by pushing exhaust backward
- Walking involves pushing Earth backward; Earth pushes you forward
- Friction force opposes motion and causes deceleration
- Tension in ropes depends on mass and acceleration
Concept of Equilibrium
- Object is in equilibrium when net force is zero
- Static equilibrium: object at rest with zero acceleration
- Dynamic equilibrium: object moving with constant velocity
- Equilibrium condition requires balanced forces
- Sum of all forces equals zero in equilibrium
Key Terms
- Inertia: Property of matter to resist change in state of motion
- Force: Push or pull that causes change in motion or shape
- Mass: Measure of amount of matter and resistance to acceleration
- Equilibrium: State when net force on object is zero and acceleration is zero
Frequently Asked Questions
Why do passengers lurch forward when a car brakes suddenly?
Due to inertia from Newton's first law, passengers continue moving forward even as the car stops. Seatbelts apply force to decelerate passengers along with the car.
If action and reaction are equal, why does a heavier object fall faster than a lighter one?
Both objects experience equal gravitational force per unit mass. But lighter objects have less mass, so they accelerate more per unit force (F equals ma). Gravity provides less total force on lighter objects, so they fall slower.
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