Physics Lesson 2: Work, Energy, & Power

Work, Energy, and Power

• Work is defined as the exertion of force on an object that causes movement in the direction of the force over a distance.
• Energy is the capacity to do work, acting as the fuel for various actions and transformations in the physical world.
• Power quantifies how quickly work is performed, measured in watts (W).

Work

• The formula for calculating work:
  Work (W) = Force (F) x Distance (d)
  • Work is measured in joules (J), force in newtons (N), and distance in meters (m).
• James Prescott Joule is noted for demonstrating that heat is a form of energy.

Example Problem of Work

• Given:
  • Force: 150 N
  • Distance: 5 m
• Calculation:
  W = 150 N * 5 m = 750 J
  • Therefore, the work done is 750 joules.

Energy Transformation

• Work can convert energy from one form to another, allowing motion and changes in position.
• The principle of energy conservation emphasizes the need to protect energy resources.

Types of Energy

Mechanical Energy

• Comprises both potential and kinetic energy associated with motion and position.

Potential Energy

• Stored energy related to an object's position or condition.
  • Gravitational Potential Energy: Depends on mass (m), gravitational acceleration (g), and height (h):
    PE = mgh
  • Elastic Potential Energy: Energy stored in stretched or compressed objects:
    PE = 1/2 kx² (k = spring constant, x = displacement)

Kinetic Energy

• Energy of an object due to its motion, calculated using the formula:
  KE = 1/2 mv² (m = mass, v = velocity)

Other Forms of Energy

• Includes heat, light, sound, electrical, chemical, and nuclear energy.

Work-Energy Theorem

• States that the work done on an object equals the change in its kinetic energy:
  W = KE - KE₀ (where KE₀ is the initial kinetic energy).

Power

• Power is the rate of doing work and is given by the formula:
  P = W/t (where t is time).
• The unit of power, watt (W), is named after James Watt, instrumental in the Industrial Revolution.
• For constant force and velocity, power can also be expressed as:
  P = Fv (Force x Velocity).