Newton's Laws of Motion

**NEWTON'S LAW OF MOTION** **NEWTON\'S FIRST LAW OF MOTION (Inertia)** **Newton\'s First Law states**: An object at rest stays at rest, and an object in motion stays in motion at constant velocity unless acted upon by a net external force. **Inertia**: the tendency of an object to resist changes...

**NEWTON'S LAW OF MOTION** **NEWTON\'S FIRST LAW OF MOTION (Inertia)** **Newton\'s First Law states**: An object at rest stays at rest, and an object in motion stays in motion at constant velocity unless acted upon by a net external force. **Inertia**: the tendency of an object to resist changes in its state of motion. ***Key Points to Remember:*** - - - **NEWTON\'S SECOND LAW OF MOTION (Force and Acceleration)** **F = m a** **Newton\'s second law states:** The net force acting on an object causes it to accelerate. The acceleration is directly proportional to the force and inversely proportional to the object\'s mass. ***Key Points to Remember:*** - - - - - - **NEWTON\'S THIRD LAW OF MOTION** **Newton\'s Third Law of Motion states**: For every action, there is an equal and opposite reaction. **Resultant Force** The resultant force is the single force that has the same effect as all the individual forces acting on an object. It is the vector sum of all the forces acting on the object. ***(How to find Resultant Force)*** 1\. ***In the same direction***: Add the magnitudes of the forces. ***Example:*** If two forces of 10 N and 5 N are acting in the same direction, the resultant force is. 10 N + 5 N = 15 N 2\. ***In opposite directions***: Subtract the magnitudes of the forces. ***Example***: If two forces of 10 N and 5 N are acting in opposite directions, the resultant force is in the direction of the larger force. 10 N - 5 N = 5 N **Forces in Equilibrium** **Equilibrium**: When the net force on an object is zero **Types of equilibrium:** **Static equilibrium**: Object is stationary. ***Example***: A book resting on a table is in static equilibrium because the forces of gravity and the table\'s upward normal force balance out. **Dynamic equilibrium**: Object moves with constant velocity. ***Example***: A car moving at a constant speed on a straight road is in dynamic equilibrium because the forces like friction and air resistance balance the forward motion. [For objects in equilibrium, all forces cancel each other out.] (**ΣF = 0**) ***Key Points to Remember:*** - - - **GENERAL PROPERTIES OF MOTION AND MASS** **Mass**: A measure of the amount of matter in an object and its resistance to acceleration (inertia). **Weight**: The force exerted by gravity on an object. Mass is constant everywhere, but weight depends on the gravitational field. ***Key Points to Remember:*** - - - **FORCE IN MOVING OBJECTS** In a moving system, several forces act on objects, affecting their motion: ***Net Force***: The total force acting on an object, determining whether it accelerates or moves at a constant speed. According to Newton's Second Law: Fnet = ma ***Types of Forces*** **Applied Force:** The force used to move the object. **Friction**: Resists motion (static or kinetic). **Gravitational Force:** Pulls objects downward. **Tension**: Force in ropes or strings. ***Example - Bus:*** A bus moving at constant speed has a balance between the applied force and friction. If the bus accelerates, the applied force must overcome friction and provide extra force for acceleration. **TENSION** Tension refers to the force transmitted through a string, rope, cable, or any other type of flexible connector. It acts along the length of the object, and is always directed away from the object that is being pulled or stretched. The force of tension is generated when an object pulls on a rope, and the rope pulls back with an equal and opposite force.  **MASS, WEIGHT, AND GRAVITY** Mass is the amount of matter in an object and does not change with location. Weight is the gravitational force acting on an object, calculated as , where is the acceleration due to gravity (***9.8 m/s² on Earth***). ***W*** = *m g* g = acceleration due to gravity m = mass **EFFECT OF GRAVITY IN OBJECTS** Gravity causes all objects to accelerate downward at the same rate (ignoring air resistance). **FREE FALL AND TERMINAL VELOCITY** **Free-fall** occurs when gravity is the only force acting on an object. **Terminal velocity** occurs when air resistance equals the gravitational force, causing the object to fall at a constant speed. **FRICTION** **Static friction**: Prevents motion; greater than kinetic friction. **Kinetic friction**: Opposes motion once the object starts moving. **MOTION IN FRICTION** Friction reduces net force, affecting acceleration or maintaining constant velocity. **Examples*:*** A sliding object slows down due to friction. A car\'s tires grip the road to prevent slipping. **MOTION IN INCLINED PLACES** **Forces and Acceleration on an Inclined Plane** On a slope, gravity has two components: **Parallel to the incline:** causes the object to slide down. **Perpendicular to the incline:** is balanced by the normal force. **Examples**: A box sliding down a ramp accelerates due to the parallel force component. The steeper the incline, the larger the parallel component and acceleration.