Work, Energy and Power
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Define work done.
The energy transferred when a force moves an object over a distance.
Equation for work done?
W = f d
Define energy.
The capacity to do work.
What is the principle of conservation of energy?
• In a closed system, the total energy remains constant. - Energy cannot be created nor destroyed, only transferred from one form to another.
Equation for Ek?
Ek = 1/2 m v2
Derive the kinetic energy equation
Use SUVAT. Check Notion for answers.
When mass is constant, what is kinetic energy directly proportional to?
Square of the speed
When speed is constant, what is kinetic energy directly proportional to?
Mass of object
Equation for GPE?
GPE = mgh
Derive the GPE equation
Check Notion.
When is Ek = GPE valid?
If there are no resistive forces
Define power.
The rate of work done.
Define 1 W
1 Joule per second
Equation for power
P = W / t
Derive the equation linking power and motion.
Check Notion.
Equation linking power and motion?
P = Fv
What conditions must be met to use the power-motion equation?
• Constant force • Constant speed (a=0) • Net force is 0 so the driving force must equal resistive forces.
Equation for efficiency?
Efficiency = useful energy / total energy X 100