General Science
1. Energy
Kinetic Energy (KE):
Comes from motion. The faster or heavier something is, the greater its KE.
Derivation: Work = Force × Distance. Since and using motion equations, you end up with .
Insight: A car at 100 km/h has 4 times more KE than the same car at 50 km/h (because velocity is squared). That’s why high-speed crashes are deadlier.
Potential Energy (PE):
Energy stored by position.
Comes from doing work against gravity (lifting).
Insight: PE is “stored work.” Water in a dam has massive PE, which turns into KE in turbines → electricity.
Thermal Energy:
Caused by microscopic motion of atoms/molecules.
Heat transfer: Conduction (solids), Convection (fluids), Radiation (waves).
Insight: When you rub your hands, mechanical energy → heat.
Electrical Energy:
Movement of charges. A power plant transforms mechanical → electrical.
Batteries store chemical PE, converted to electricity in circuits.
Sound Energy:
Mechanical waves traveling through air, water, or solids.
Higher amplitude = louder sound; higher frequency = higher pitch.
Law of Conservation of Energy:
No energy disappears, it only changes form.
Example: Roller coaster → PE at the top, KE as it falls, sound + heat due to friction, but the total energy stays constant.
2. Applications of Physics
Health and Safety:
Seatbelts, airbags (momentum control).
X-rays, MRI (electromagnetism).
Work Productivity:
Robotics, electrical machines, hydraulics for heavy lifting.
Leisure:
Sports science (motion analysis), theme parks (energy conversions), VR and gaming (optics + sound).
3. Motion
Translational Motion: Straight-line movement.
Equations:
Rotational Motion: Motion around an axis.
Equations mirror linear ones:
Angular displacement () ↔ linear displacement ()
Angular velocity () ↔ linear velocity ()
Angular acceleration () ↔ linear acceleration ()
Key Connection:
v = r\omega
4. Simple Machines
Purpose: Trade force for distance. You don’t do less work, you just make it easier.
Lever:
Formula: .
Classes depend on fulcrum, load, and effort placement.
Inclined Plane:
Less force needed: .
Wedge: Splits or cuts by converting force into sideways motion.
Wheel and Axle: Small effort moves a large load by rotation.
Pulley:
Single fixed pulley changes direction, not force.
Multiple pulleys increase MA.
Efficiency:
Always < 100% because of friction.
Improved by lubrication, better materials, streamlined design.
Compound Machines: Combinations for bigger advantage.
Can opener (3 simple machines combined).
Bicycle (gears + wheels + levers).
Crane (pulley + lever).
5. Hydraulics
Pascal’s Principle: Pressure applied to a fluid is transmitted equally in all directions.
Formula:
F_1/A_1 = F_2/A_2
Applications: Car brakes, lifts.
6. Momentum
Momentum (p): Inertia in motion.
Formula: .
Conservation Law:
Momentum before collision = momentum after (if no external force).
Example: Billiard balls, rocket propulsion.
7. Fluids
Archimedes’ Principle:
Buoyant force = weight of displaced fluid.
Explains why boats float and submarines sink/rise.
Density:
.
If object density < fluid density → it floats.
Fluid Displacement:
Volume of displaced water = volume of submerged part of object.
Example: Measuring irregular solids (Eureka experiment).
✨ Deeper Insights
Energy is currency: Think of energy like money—never lost, only spent, saved, or changed form.
Motion symmetry: Linear ↔ Rotational equations are almost identical.
Simple machines don’t reduce work, they make it manageable.
Hydraulics multiply force but need incompressible fluids.
Momentum explains why safety devices (helmets, airbags) are crucial.
Archimedes’ principle + density = floating ships despite their huge weight.