TOPIC 5: WORK ENERGY POWER Flashcards
[Definition] Work done
Work done by a force is the product of the force and the displacement in the direction of the force.
[Formula] Work done
W = Fs cosθ
[Definition] 1 Joule
1J is defined as the work done when a force of 1N moves its point of application through a distance of 1m in the direction of the force.
2 types of work done
Positive work done: Mechanical energy is being transferred to the body
Negative work done: Mechanical energy is being transferred away from the body
Work done by a varying force
The area under a Force-Displacement graph
[Formula] Work done by an expanding gas
W = pΔV
W = F(s)(cosθ)
= F(Δx)(1)
= pA(Δx)
= p(AΔx)
= pΔV
p refers to external pressure, Assuming external pressure is constant
If not constant, find area under Pressure-Volume graph
[Definition] (Translational) Kinetic Energy
Kinetic energy is the energy possessed by a mass due to its speed or motion.
[Formula] Kinetic Energy
Ek = 1/2 mv²
[Definition] Gravitational Potential Energy
Gravitational potential energy is the energy of a mass due to its position in a gravitational field.
[Formula] Gravitational Potential Energy
ΔEp = mgΔh
*It isn’t an absolute value for the GPE of a body
[Definition] Elastic Potential Energy
Elastic potential energy is the ability to do work by the object when it is deformed
*Deformed can mean change in shape, being compressed, being stretched, or being strained
[Formula] Elastic Potential Energy
Elastic Ep = 1/2kx²
*Only if the spring obeys Hooke’s Law
Principle of Conservation of Energy
- Energy cannot be created or destroyed
- Energy can only be converted from one from to another
- The total energy of an isolated system remains constant
[Formula] PCOE
Total initial energy = Total final energy + WDAF
Decrease in energy = Gain in energy + WDAF
[Definition] Power
Power is the work done per unit time
