Work, Energy & Power Flashcards
Define the work done on an object by a constant force F
FΔxcosθ , where F is the magnitude of the force,
Δx is the magnitude of the displacement and θ is the angle between the force and the displacement. (Work done is a transfer of energy.)
State the work-energy theorem:
The work done on an object by a net force is equal to
the change in the object’s kinetic energy OR the work done on an object by a net force is equal to the change in the object’s kinetic energy.
work-energy theorem in symbols:
Wnet = ΔK = Kf - Ki
Conservative force
a force for which the work done in moving an object between 2 points is independent of path taken.
Examples are gravitational force, the elastic force in a spring and electrostatic forces (coulombic forces).
Non-conservative force
a force for which the work done in moving an object between 2 points depends on the path taken. Examples are frictional force, air resistance, tension in a chord, etc.
The principle of conservation of mechanical energy:
The total mechanical energy (sum of gravitational potential energy and kinetic energy) in an isolated system remains constant.
What is an isolated system
A system is isolated when the net external force (excluding the gravitational force) acting on the system is zero.
Solve conservation of energy problems using the equation:
Wnc = ΔEk + ΔEp
Power
the rate at which work is done or energy is expended
energy
the ability to do work (joules)
gravitational potential energy (Ep)
energy an object possesses due to its position relative to reference point.
kinetic energy (Ek)
energy object has as a result of its motion
mechanical energy (Em)
the sum of gravitational potential and kinetic energy of object at point
law of conservation of energy
energy cannot be created nor destroyed, merely transferred
What quantity is work
scalar quantity
