Science Quarter 3 Review Notes

• Friction: A force that opposes motion between two surfaces in contact.

  • Divided into:

    • Static friction: Prevents motion.

    • Kinetic friction: Slows down moving objects.

  • Depends on:

    • Surface textures.

    • Normal force pressing surfaces together.

  • Applications:

    • Brakes in vehicles.

    • Traction when walking.

• Gravity: A universal force of attraction that pulls objects toward each other.

  • Strength is:

    • Proportional to the masses of the objects.

    • Inversely proportional to the square of the distance between them.

  • Described by:

    • Isaac Newton's Law of Universal Gravitation, fundamental in understanding celestial motions and physics.

• Energy: The capacity to do work, existing in various forms:

  • Kinetic energy: Energy of motion.

  • Potential energy: Stored energy.

  • Thermal energy: Energy associated with temperature.

  • Chemical energy: Energy stored in chemical bonds.

  • Nuclear energy: Energy released during nuclear reactions.

  • Electrical energy: Energy caused by the movement of electrons.

  • Mechanical energy: The sum of kinetic and potential energy in an object.

  • Governed by the Law of Conservation of Energy:

    • Energy cannot be created or destroyed, only change forms.

• Transformation of Energy: Involves changing one form of energy into another.

  • Examples:

    • Chemical energy to thermal energy during combustion.

    • Electrical energy to kinetic energy in motors.

  • Crucial in applications such as:

    • Powering machines and vehicles.

    • Biological processes like metabolism.

Simple Machines

Fundamental mechanical devices that facilitate work by either amplifying force or altering its direction. The six classical simple machines are:

1. Lever

   • Comprises a beam that rotates around a fulcrum.

   • Capable of amplifying force or changing its direction.

   • Common uses include seesaws and crowbars.

2. Wheel and Axle

   • A large wheel attached to a smaller axle.

   • Minimizes friction, making it easier to move objects.

   • Found in examples such as doorknobs and bicycles.

3. Pulley

   • A wheel designed with a groove to accommodate a rope or cable.

   • Changes the direction of force and can provide force multiplication.

   • Used in applications like flagpoles and cranes.

4. Inclined Plane

   • A flat surface set at an angle.

   • Enables lifting heavier objects with reduced effort.

   • Commonly seen in ramps and slides.

5. Wedge

   • A double inclined plane utilized to move through a substance.

   • Effective for splitting or cutting through objects with applied force.

   • Examples include axes and knives.

6. Screw

   • An inclined plane twisted around a cylinder.

   • Converts rotational movement into linear motion.

   • Common in bolts and jar lids.