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sscience

ENERGY

Potential Energy (PE):

- Formula: PE = mgh

- Unit: Joules (J)

Gravitational Potential Energy (GPE):

- Formula: GPE = mgh

- Unit: Joules (J)

Elastic Potential Energy:

- Formula: PE_elastic = 1/2 k x^2

- Unit: Joules (J)

Mechanical Energy (ME):

- Formula: ME = PE + KE

- Unit: Joules (J)

Efficiency:

- Formula: Efficiency = (Output Work / Input Work) * 100%

- Unit: Percentage (%)

Mechanical Advantage:

- Formula: MA = (Output Force / Input Force)

UNITS TO KNOW

Mass:

- Unit: Kilograms (kg)

Energy or Work:

- Unit: Joules (J)

Velocity:

- Unit: Meters per second (m/s)

Gravity:

- Unit: Meters per second squared (m/s²)

Height:

- Unit: Meters (m)

MECHANICAL ENERGY and CONSERVATION OF ENERGY

- ME = PE + KE

- PE = mgh

- KE = 1/2 * mv^2

- g = 9.81 m/s^2

Efficiency and Mechanical Advantage

- Efficiency = (Output Work / Input Work) * 100%

- MA = (Output Force / Input Force)

Simple Machines:

  1. Incline Plane: Transfers force.

  2. Pulley: Changes force direction or amount.

  3. Lever: Changes force applied or distance.

  4. Screw: Increases distance and decreases applied force.

  5. Wedge: Increases force over a shorter distance.

  6. Wheel and Axle: Transfers force, reduces friction.

Energy Conversion: Energy is converted from one form to another, maintaining the total amount of energy. Examples:

  • Roller coaster: Potential to kinetic energy.

  • Running: Chemical to mechanical energy.

  • TVs: Electrical to heat and light energy.

  • Car: Chemical to thermal and mechanical energy.

  • Wind turbine: Kinetic to mechanical to electrical energy.

WORK SCENARIOS

  1. Waiter carrying a tray of meals: No work (perpendicular displacement).

  2. You lifting your phone to take a selfie: Positive work (force and displacement in the same direction).

  3. Among Us character pushing the button: Positive work (force and displacement in the same direction).


ENERGY

Potential Energy: Energy of an object due to its position, shape, or condition. Also known as stored energy.

Gravitational Potential Energy: Type of potential energy due to an object's position in a gravitational field.

Elastic Potential Energy: Type of potential energy stored in elastic or stretchy materials.

Chemical Potential Energy: Type of potential energy stored in substances such as batteries or food.

Kinetic Energy: Energy due to the motion of an object.

Thermal Energy: Type of kinetic energy; energy of randomly moving atoms.

Sound Energy: Type of kinetic energy; energy of moving air particles.

Electrical Energy: Type of kinetic energy; energy of moving electrons.

Mechanical Energy: The sum of kinetic and potential energy; the energy of an object's motion and position.

Conservation of Energy: The total amount of energy remains constant in a system; energy cannot be created or destroyed, only transferred or transformed.

Simple Machine: Device that reduces work by utilizing one form of movement.

Compound Machine: Combination of one or two simple machines that reduce work.

Output Work: The work produced by a simple machine.

Input Work: The work applied to the simple machine.

Efficiency: Measure of how much energy is lost due to friction, expressed as a percentage.

Mechanical Advantage: Measure of a machine's effectiveness at increasing force or distance; has no unit.

UNITS TO KNOW

Mass: Kilograms

Energy or Work: Joules

Velocity: Meters per second (m/s)

Gravity: 9.8 meters per second squared (m/s²)

Height: Meters

Mechanical Advantage: No unit

Efficiency: Percentage

Force: Newtons (N)

CONCEPTUAL QUESTIONS

Higher= higher potentil energy

Machines:

  • Tow Truck: Compound machine, includes a pulley, wheel and axle, and screw; reduces work by changing force direction.

  • Slide: Simple machine (inclined plane); reduces work by changing force direction.

  • Roller Skates: Simple machine (wheel and axle); reduces work by transferring force.

  • Scissors: Compound machine, includes two inclined planes and a screw; reduces work by increasing force.

  • Class 1: Fulcrum between input and output force (e.g., see-saw).

  • Class 2: Output force between fulcrum and input force (e.g., wheelbarrow).

  • Class 3: Input force between fulcrum and output force (e.g., tweezers).

  1. Car driving down the road: Kinetic energy.

  2. Arrow drawn in an archery tournament before firing: Elastic energy.

  3. Radio playing: Sound energy.

  4. Sun shining: Solar energy.

  5. Roller Coaster sitting on top of the hill: Potential energy.

  6. Battery in a remote not being used: Chemical energy.