Physics PDF - Force, Balanced and Unbalanced Forces
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This document provides an introduction to forces in physics. It describes balanced and unbalanced forces, and their effects on objects, along with examples. The document also explains the first law of motion and inertia.
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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
