Understanding Work and Power

• When a task uses energy, work is being done.
• The rate of work done is measured using power.
• Power relates to work by measuring the amount of work done per unit of time.

Work

• Work, in a scientific sense, requires displacement.
• Work is the measurement of the energy used to perform a task.
• Work is solved by using the equation Force x Distance.
• The units of work are Newton-meters (Nm) or Joules (J).
• If a 200 N object is lifted 10m, the work done is 2000 Nm or J.
• If a 30 N bucket is lifted 5 m, the work done is 150 Nm or J.
• Tables don't do work because they don't move mass through a distance.
• If student A moves a 10-kg box 2 meters and student B moves a 20-kg box 1 meter, both students do the same amount of work.
• 20 J of work is done by each student.

Power

• Power is the amount of work done per unit of time, or work divided by time.
• The standard unit of power is Joules per second (J/s) which is also known as watt (W).
• If a task requires 400 J of work and takes 20 seconds to complete, the power for this task is 20 J/s or W.

Energy

• Energy is the ability to perform work or to change an object
• Energy has the same units as work, which are Joules (J)

Forms of Energy

• Potential energy is energy that is stored in the position, or structure, of an object.
• Forms of potential energy: chemical, nuclear, magnetic, and electrical energy
• Kinetic energy is the energy of a moving object.
• Forms of kinetic energy: heat, electricity, sound, and light.
• Periodic motion is vibrating like a spring, where energy changes back and forth from potential to kinetic.

Law of Conservation of Energy

• Energy can neither be created nor destroyed, it is only converted from one form of energy to another.
• Example: Friction converts kinetic energy into heat energy.
• Example: Hydroelectric dams convert kinetic energy into electricity.