Work, Power, and Energy in Physics

This page provides a comprehensive overview of key concepts in physics related to work, power, and energy, tailored for 7th-grade students. It includes essential formulas, examples of simple machines, and the principle of energy conservation.

Definition: Work is defined as the product of force and displacement in the direction of the force.

The formula for work is presented as:

W = F • S

Where:

• W is work
• F is force
• S is displacement

Vocabulary: The unit of work is the Joule (J), which is equivalent to 1 Newton-meter (1 N•m).

The concept of power is introduced next, defined as the rate of doing work:

P = W / t

Where:

• P is power
• W is work
• t is time

Vocabulary: The unit of power is the Watt (W), which is equivalent to 1 Joule per second (1 J/s).

The page then covers different forms of energy:

1. Kinetic Energy (Ek): The energy of motion, given by the formula Ek = (1/2)mv²
2. Potential Energy (Ep): The energy due to position or configuration, given by Ep = mgh for gravitational potential energy
3. Mechanical Energy (Em): The sum of kinetic and potential energy, Em = Ek + Ep

Highlight: Understanding these energy forms is crucial for grasping the concept of energy conservation in mechanical systems.

The document illustrates several simple machines to demonstrate the application of work and energy principles:

1. Two-sided Lever (e.g., seesaw): F₁ • l₁ = F₂ • l₂
2. Wheel and Axle: F • l = Q • r
3. One-sided Lever (e.g., wheelbarrow): Uses the same principle as the two-sided lever
4. Inclined Plane: W = Q • h (work done) and W = F • L (force applied along the plane)
5. Fixed Pulley: Changes the direction of force but not its magnitude

Example: A seesaw demonstrates the principle of moments, where the product of force and distance on both sides must be equal for balance.

Finally, the page introduces the principle of conservation of mechanical energy:

1. In closed systems with no external forces: Em remains constant
2. With external forces: Change in Em equals the work done by external forces

Highlight: The conservation of energy principle is fundamental in physics and helps explain various phenomena in mechanics and beyond.