Mechanics - Energy Flashcards
Define energy
Energy is the capacity to do work
What are the units of energy?
Joules (J)
What type of energy does an object have when it is up high above the ground?
Gravitational potential energy
What is the formula for gravitational potential energy?
Ep = mgh (m = mass, g = gravity of 10ms-2, h = height)
What type of energy does an object have when it is moving?
Kinetic energy
What is the formula for kinetic energy?
Ek = 1/2mv2 (v = velocity, m = mass)
What type of energy does friction create?
Heat/Radiant energy
What type of energy doe food and fuels have?
Chemical potential energy
What type of energy travels in waves?
Sound energy
When an object falls from a given height and assuming there is no friction, what is the relationship between the amount of gravitational potential energy at the initial height and the amount of kinetic energy the object has when it hits the ground?
The will be the same: Ep = Ek which is conservation of energy
Why is reality doe Ep not equal Ek
As an object falls, it collides with air particles which creates friction/drag. This means that not all the gravitational potential energy is converted into kinetic energy. Some is converted into heat energy. Therefore the velocity of an object will be less than expected
Define work
When energy is converted from one form to another
What is the formula for work?
W = F x d
Compare the amount of work done lifting an object to a given height to the amount of gravitational potential energy that object will have at that height.
They will be the same. Ep = mgh and W = F x d. The mg part is the same as the F (weight force) and h (height is the same as distance (d) lifted
Define power
The rate at which work is done (how quickly energy is converted from one form to another)
