Force Short notes and Selected PYQs | SmartScience ICSE Class 10

Force: A push or pull that changes or tends to change the state of rest or uniform motion of a body. SI unit: Newton (N).
Types of Force: Contact forces (friction, tension, normal force) and non-contact forces (gravitational, magnetic, electrostatic).
Effects of Force: Can change the speed, direction, shape, or state of rest of a body.
Balanced Forces: Forces that cancel each other out, resulting in no change in motion.
Unbalanced Forces: Forces that do not cancel out, resulting in acceleration.

Moment of Force: The turning effect of a force about a pivot point. Also called torque.
Formula: Moment = Force × Perpendicular Distance from pivot. Unit: Newton-meter (N·m).
Clockwise and Anticlockwise Moments: Moments causing rotation in different directions.
Principle of Moments: For a body in equilibrium, the sum of clockwise moments equals the sum of anticlockwise moments about any point.
Applications: Seesaws, door handles, spanners, and other rotating systems.

Centre of Gravity: The point at which the entire weight of a body appears to act.
Stability: A body is stable when its centre of gravity is low and base is wide.
Types of Equilibrium: Stable (returns to original position), unstable (moves away), and neutral (remains in new position).
Factors Affecting Stability: Position of centre of gravity and area of base of support.

Uniform Circular Motion: Motion in a circular path at constant speed but changing velocity due to continuously changing direction.
Centripetal Force: The force directed towards the centre that keeps an object moving in a circular path.
Formula: F = mv²/r, where m = mass, v = velocity, r = radius.
Examples: Motion of satellites, turning of vehicles, motion of electrons around nucleus.

Force