Work, Energy, and Power: Crash Course Physics #9
Work and Energy
In this video, we explore the definition of work in physics and how it connects to the conservation of energy. We also learn about power and two types of energy: kinetic and potential.
Definition of Work
- Work is done when a force is applied over a certain distance to a system.
- The amount of work done is equal to the force applied times the distance moved.
- If the force is not in the same direction as the movement, you must use trigonometry to calculate the parallel component of force.
Varying Force
- When dealing with varying forces, you must integrate them relative to distance moved.
- Joules are used as units for both work and energy.
Kinetic Energy
- Energy is defined as the ability to do work.
- Kinetic energy is the energy of motion and can be calculated using mass and velocity.
Potential Energy
- Potential energy is stored energy that can be converted into kinetic energy.
- Gravitational potential energy depends on an object's height above ground level.
Potential Energy and Work
This section explains the concept of potential energy and how it relates to work.
Gravitational Potential Energy
- Potential energy is energy that could be used to do work.
- Gravitational potential energy is the potential energy that comes from gravity.
- The formula for calculating gravitational potential energy is mgh.
Spring Potential Energy
- Spring potential energy is specific to springs.
- Hooke's law states that the force of a spring is equal to the distance by which it's either compressed or stretched, times a constant called k.
- The formula for calculating spring potential energy is 1/2kx^2.
Conservative vs Non-conservative Systems
This section explains the difference between conservative and non-conservative systems.
Non-conservative Systems
- Non-conservative systems can lose energy through work, such as when friction generates heat.
Conservative Systems
- Conservative systems don't lose energy through work.
- A simple pendulum is an example of a conservative system where kinetic and potential energies add up to the same number at any given point in its motion.
Power
This section defines power and how it's measured.
Average Power
- Average power is defined as work over time, measured in Watts (Joules per second).
- The formula for average power output is work divided by time.
Equations for Work and Power
This section covers the two equations used to describe work and power.
Two Equations for Average Power
- The force used to pull an object multiplied by its average velocity gives the average power output.
- The two equations for average power are describing the same relationship, but using different qualities.
Energy and Kinetic vs Potential Energy
This section covers energy, kinetic energy, potential energy, and how they play into conservative and non-conservative systems.
Understanding Energy
- Energy is the ability to do work.
- Kinetic energy is the energy of motion.
- Potential energy is stored energy that can be converted into kinetic energy.
- Conservative systems conserve mechanical energy while non-conservative systems do not.
Two Different Equations for Power
This section covers two different equations for power.
Calculating Power
- Power is calculated by dividing work by time or multiplying force by velocity.
- These equations are useful in understanding how energy moves around in a circuit.
Credits
This section acknowledges those who helped produce Crash Course Physics.
Production Team
- Crash Course Physics was produced in association with PBS Digital Studios.
- Other amazing shows on their channel include The Art Assignment, PBS Idea Channel, and PBS Game Show.
- Filmed in the Doctor Cheryl C. Kinney Crash Course Studio with help from an amazing production team and graphics team at Thought Cafe.