Work, Energy and Power Flashcards
Work
The work done on an object by a constant force F as FΔx cosθ, where F is the magnitude of the force, Δx the magnitude of the displacement, and θ the angle between the force and the displacement.
Net Work
The net work done on an object is the total work done by all the forces acting on the object.
Positive Net Work
When the net work done on a system is positive, it means that work is being done on the system, increasing its energy.
Negative Net Work
When the net work done on a system is negative, it means that work is being done by the system, decreasing its energy.
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. In symbols: Wnet = ΔK = Kf - Ki.
Conservative Force
A force for which the work done in moving an object between two points is independent of the path taken.
Examples include gravitational force, elastic force in a spring, and electrostatic forces.
Non-Conservative Force
A force for which the work done in moving an object between two points depends on the path taken.
Examples include frictional force, air resistance, and tension in a chord.
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 when the net external force acting on the system is zero.
Power
Power is defined as the rate at which work is done or energy is expended. In symbols:
P = W/t.
