Work, Energy & Power Flashcards
Definition of work done
The work done by a force on a body is the product of that force and the displacement of the body in the direction of the force.
Formula of work done
W = F s cos θ
What is the unit of work and is it scalar or vector?
Joule(J)
Scalar
What is one joule?
A joule is the work done by a force of 1 newton when its point of application moves through a displacement of 1 metre in the direction of the force.
Definition of energy and work
Energy is the ability to do work.
Work is a process in which energy is transferred from one object to another through the action of a force on an object.
How do you find work done from F-s graph?
Area under F-s graph
How do you find work done by a gas at constant external pressure?
W = p(Vf - Vi)
Definition of kinetic energy
Kinetic energy is a type of energy which a body possesses by virtue of its motion.
What is the work-energy theorem?
The work done on a rigid body by the resultant force is always equal to the change in the kinetic energy of the body.
Definition of gravitational potential energy
Gravitational potential energy is the energy possessed by a mass by virtue of its position in a gravitational field.
Definition of electric potential energy
Elastic potential energy is the energy possessed by an electric charge by virtue of its position in an electric field produced by other electric charges.
Definition of elastic potential energy
The energy of a system of atoms by virtue of their positions where the particles experience short-range interatomic attractive or repulsive forces.
How do you find elastic potential energy from a force-extension graph?
Area under graph
Formula for elastic potential energy
W = 1.2 kx^2(if Hooke’s law is being obeyed)
Definition of potential energy
Potential energy is the energy stored in an object due to its position, shape or state.
What is the relationship between force and potential energy?
F = -dU/dr
F is force and U is potential energy
Definition of dissipative forces
Dissipative forces are forces whereby energy is lost from a system where motion takes place.
Examples of dissipative forces
Kinetic frictional forces and viscous forces
Definition of Principle of Conservation of Energy
The principle of conservation of energy states that the total energy of an isolated system is constant. Energy cannot be created or destroyed, but can be transferred from one form to another.
Formula for Principle of Conservation of Energy
KE initial + PE initial + E supplied = KE final + PE final + E lost
Loss in KE = Gain in PE
Definition of power
Power is defined as the rate of work done or energy transfer.
Formula of power
P = dW/dt, P = Fv
P = W/t (if work done is constant)
Unit of power
Watt(W) or joule per second( J/s)
Definition of efficiency
It is the rate of useful energy output to the total energy input
