Jaza

Definition:Centripetal force is the force that keeps an object moving in a circular path. it acts toward the center of the circle around which the object is moving.

Why things revolve around Earth without collapsing?

1. Gravitational Force = Centripetal Force

• The Earth’s gravity pulls the Moon, satellites, or any orbiting body toward its center.

• This pull acts as the centripetal force, keeping the object in orbit.

• The object’s speed prevents it from falling straight down.

Weight and Mass

• Mass is the amount of matter in an object; it never changes with location.

• Weight is the gravitational force on an object: W=m×gW =

• Unit of weight → Newton (N); unit of mass → kilogram (kg).

• Weight changes with gravity; mass does not.

Gravity

• Definition: Density = mass per unit volume.

• Symbol: ρ\rhoρ (rho).

• Formula: ρ=mV\rho = \frac{m}{V}ρ=Vm​.

• SI Unit: kg/m³ (also g/cm³).

• Concept: Denser objects have more mass packed into the same space.

• Measuring density: Measure mass with a balance. Measure volume (by formula for regular objects, displacement for irregular ones).
  

• Melting: The change of a solid into liquid at a fixed temperature (melting point). Heat energy is absorbed but temperature remains constant during the change.

• Boiling: The rapid change of liquid into gas at a fixed temperature (boiling point). Heat is absorbed, bubbles form throughout the liquid.

• Evaporation: Slow change of liquid into gas at any temperature (below boiling point), occurs only at the surface. Faster when temperature, surface area, and airflow are higher, or humidity is lower.