Work, Energy and Power in A Level Physics AS

Work, Energy and Power Concepts

Energy

Energy is a fundamental concept in physics and comes in various forms:

• Kinetic Energy - Energy of motion possessed by an object with mass and velocity
• Gravitational Potential Energy - Energy stored in an object due to its position in a gravitational field
• Elastic Potential Energy - Energy stored in a deformed elastic object like a spring

Conservation of Energy

The total energy of an isolated system remains constant - it is just transferred between different forms. This principle underpins many applications in mechanics.

Work and the Work-Energy Theorem

Work is done when a force displaces an object over a distance. The work-energy theorem states that the work done on an object is equal to the change in its kinetic energy.

Example: Work and Kinetic Energy

Problem: A 2 kg object accelerates from 2 m/s to 5 m/s due to a constant force of 10 N. Calculate the work done.

Solution:

1. Initial KE = (1/2)mv₀² = (1/2) × 2 × 2² = 4 J
2. Final KE = (1/2)mv² = (1/2) × 2 × 5² = 25 J
3. Work done = Change in KE = 25 J - 4 J = 21 J

Power

Power is the rate of energy transfer or work done. The power developed is equal to the work done per unit time:

Power = Work done / Time taken

Understanding these concepts allows solving problems involving mechanical systems, energy transformations, and efficiency calculations.