1. Work and Energy

2. Work is done on an object when a force causes a displacement of the object.
Work is done only when components of a force are parallel to a displacement.

3. Work = Force x displacement
W = FΔx or W = Fd
In the SI system, the units of work are joules:
As long as this person does not lift or lower the bag of groceries, he is doing no work on it. The force he exerts has no component in the direction of motion.

4. Kinetic Energy Kinetic Energy
The energy of an object that is due to the object’s motion is called kinetic energy.
Kinetic energy depends on speed and mass.
Jet
Roller coaster

5. net work = change in kinetic energy
Work-Kinetic Energy Theorem:
The net work done by all the forces acting on an object is equal to the change in the object’s kinetic energy.
The net work done on a body equals its change in kinetic energy.
Wnet = ∆KE
net work = change in kinetic energy

7. Potential Energy
Potential Energy is the energy associated with an object because of the position, shape, or condition of the object.

9. Potential Energy
In raising a mass m to a height h, the work done by the external force is:
Gravitational potential energy is the potential energy stored in the gravitational fields of interacting bodies.

10. Elastic potential energy is the energy available for use when a deformed elastic object returns to its original configuration.
The symbol k is called the spring constant, a parameter that measures the spring’s resistance to being compressed or stretched.

11. Elastic Potential Energy

12. Energy Mechanical Non-mechanical Kinetic Potential
Gravitational Elastic

13. Mechanical Energy
Mechanical energy is the sum of kinetic energy and all forms of potential energy associated with an object or group of objects.
ME = KE + ∑PE
Mechanical energy is often conserved.
MEi = MEf
initial mechanical energy = final mechanical energy (in the absence of friction)

14. Rate of Energy Transfer
Power is a quantity that measures the rate at which work is done or energy is transformed.
P = W/∆t
power = work ÷ time interval
An alternate equation for power in terms of force and speed is
P = Fv
power = force × speed
Power is measured in Watts.
One watt = 1 J/s
1HP = ~745W

15. The Unit HP was created by James Watt
Used to market steam powered machines and to calculate payments when working on commission.
Most people run on .1HP