PHYSI.pdf

‭ ORCE,‬ F ‭A push or a pull on a body is called force. Forces are used in everyday actions like pushing,‬ ‭pulling, lifting, stretching etc. A force cannot be seen. A force can be judged only by the effects‬ ‭which it can produce in the objects around us.‬ ‭Force is a vector quantity as it ha...

‭ ORCE,‬ F ‭A push or a pull on a body is called force. Forces are used in everyday actions like pushing,‬ ‭pulling, lifting, stretching etc. A force cannot be seen. A force can be judged only by the effects‬ ‭which it can produce in the objects around us.‬ ‭Force is a vector quantity as it has magnitude and direction. It is represented by F.‬ ‭SI unit – Newton [N]‬ ‭BALANCED FORCE,‬ ‭ hen the total applied force is zero, the forces are called‬‭balanced forces‬‭. These forces do not‬ W ‭change the motion of an object. Balanced forces are equal in strength but act in opposite‬ ‭directions. However, they‬‭can change the shape‬‭of an object.‬ ‭Example‬‭: When you press a balloon from both sides, its shape and size change.‬ ‭ NBALANCED FORCES‬‭,‬ U ‭If the resultant of applied forces is greater than zero, the forces are called unbalanced‬ ‭forces.Unbalanced forces can bring about the following effects.‬ ‭1. Move a stationary object.‬ ‭2. Increase or decrease the speed of a moving object.‬ ‭3. Stop a moving object.‬ ‭4. Change the shape or size of an object.‬ ‭First law of motion‬ ‭An object remains in a state of rest or uniform motion in a straight line unless compelled to‬ ‭change that state by an applied force.‬ ‭Inertia‬ I‭nertia is the tendency of an object to stay at rest or keep moving at the same speed unless‬ ‭something changes it.‬ ‭ xample‬‭: When you hit a carpet, the dust particles come out. Both the carpet and dust were at‬ E ‭rest. When you hit the carpet, it moves, but the dust stays still due to its inertia of rest, making it‬ ‭fall out of the carpet.‬ ‭Applications of Newton's First Law of Motion (Simplified)‬ ‭1.‬ ‭Passengers fall forward when a moving car suddenly stops‬‭:‬ ‭○‬ ‭Explanation‬‭: When the car slows down, our body still tries to keep moving‬ ‭forward due to the‬‭inertia of motion‬‭, causing passengers‬‭to fall forward.‬ ‭2.‬ ‭Passengers fall backward when a bus starts suddenly‬‭:‬ ‭○‬ ‭Explanation‬‭: When the bus starts moving, the passenger's‬‭feet move with the‬ ‭bus, but the rest of the body stays still due to‬‭inertia‬‭of rest‬‭, causing the‬ ‭passenger to fall backward.‬ ‭3.‬ ‭Passengers are thrown to one side during a sharp turn‬‭:‬ ‭○‬ ‭Explanation‬‭: As the car turns, our body wants to keep‬‭moving in a straight line‬ ‭due to‬‭inertia‬‭. When the car changes direction, we‬‭feel like we are thrown to the‬ ‭side because our body resists the change in motion.‬ ‭Inertia and mass‬‭.‬ ‭Inertia is a natural tendency of an object to resist a change in its state of motion or of rest. The‬ ‭mass of an object is a measure of its inertia‬ ‭Momentum‬ ‭The term momentum was introduced by Newton which combines the object’s mass and its‬ ‭velocity.‬ ‭The momentum ‘p’ of an object is defined as the product of its mass, ‘m’ and velocity, ‘v’‬ ‭p =mv‬ ‭SI unit → kg m/s‬ I‭t is a vector quantity as it has both direction and magnitude its direction is same is that of‬ ‭velocity‬ ‭ ewton's‬‭Second Law of Motion‬‭states that the rate of change of momentum of an object is‬ N ‭directly proportional to the unbalanced force applied, and it occurs in the direction of the applied‬ ‭force.‬ ‭Applications of Newton's Second Law of Motion (Simplified)‬ ‭.‬ 1 ‭2.‬ ‭3.‬  ‭.‬ 4 ‭5.‬ ‭Catching a fast-moving cricket ball‬‭:‬ ‭○‬ ‭Explanation‬‭: A fielder pulls his hands back while catching the ball to increase‬ ‭the time it takes for the ball to stop. This reduces the ball's acceleration, which‬ ‭decreases the force on his hands, making it easier to catch.‬ ‭6.‬ ‭High jump athletes landing on a cushioned or sand bed‬‭:‬ ‭○‬ ‭Explanation‬‭: The cushion or sand bed increases the‬‭time it takes for the athlete‬ ‭to stop after landing. This reduces the rate of change of momentum and thus‬ ‭lowers the force on the athlete's body, preventing injury.‬ ‭7.‬ ‭Karate player breaking a slab of ice‬‭:‬ ‭○‬ ‭Explanation‬‭: A karate player strikes quickly to reduce‬‭the time of impact. This‬ ‭increases the rate of change of momentum in a short time, applying a large force‬ ‭and breaking the ice slab.‬ ‭ hese examples illustrate how changing the time over which force is applied affects the‬ T ‭outcome, as described by the second law of motion.‬ ‭4o‬