5. work, energy and power Flashcards
When is work done?
When energy is transferred
What is the equation for work done?
W = Fx
Work done = force x displacement
What are some assumptions made with W = Fx?
Force is a fixed value in any calculations, constant or average force.
Equations assume that the direction of the force is in the same direction and along the same line of movement.
Equation gives the definition of a Joule: “One Joule is the work done when a force of 1N moves through a distance of 1m.”
What’s the equation of work done when the force is not in the direction of motion?
W = Fx cosθ
What is the equation for power and velocity?
Power = force x velocity
What is the equation of kinetic energy?
0.5 x m x v²
What is the equation for GPE?
mgh
What is the equation for efficiency?
Useful energy output
——————————— x 100
Total energy input
What is the equation of energy transfer for falling objects?
mgh = 0.5 x m x v²
What is the principle of conservation of energy?
Total energy of a closed system remains constant as energy cannot be created or destroyed, but can be transferred.
Define Work done?
The product of the magnitude of a force and the distance moved by the object in the direction of the force.
Unit: Joules
Define Kinetic Energy and give its SI base units.
KE: energy associated with the motion of an object with mass.
SI base units: kg m²s⁻²
Define Gravitational Potential Energy.
Energy of an object due to its position in a gravitational field.
Define Elastic Potential Energy.
Energy stored by an object as a result of a reversible change in its shape.
What is the rate of work done equal to?
Power
What is the equation for power?
P = E/t
