Energy Flashcards
2 types of mechanical energy
Kinetic and potential
Describe kinetic energy
Energy something has bc its moving
Kinetic energy equation
KE = 1/2mv^2
Describe potential energy
Energy due to position it has the potential to move and ha ve kinetic energy
Usually something being held up or a spring squeezed
Gravitational potential energy equation
Ug = mgh
Elastic potential energyequation
Ue = 1/2 kx^2
Uses hookes law when something is deformed it wants to go back to the original shape
What is the law of conservation of energy, what does that tell us about kinetic and potential energy mathematically
Energy cant be created or destroyed only transformed therefore change in energy will be zero
So initial kinetic + potential energy = final kinetic + potential energy
How can energy be transferred within a closed system explain this mathematically
Work and heat
Work + heat = change in energy
Values are negative if work or heat are lost
What is the work energy theorem
Often in physics no heat lost or gained so simply put
Change in energy = work
What is conservative force
Work done results in energy stored available for kinetic energy. Path independent so it does not change the total mechanical energy of the system
* associated with potential energy ex. Gravity, elastic, electric
What is non conservative energy
Energy is “lost” and no longer available as kinetic energy for that system , path dependent removing energy to reduce the total mechanical energy of the system
Ex. Friction force, air resistance, human exertion
W = Fdcos
How do we know if work is +/-/0 and what do those different values of work mean
Force and distance in same direction means positive work so the system is gaining energy from the surroundings
If force and distance are in opposite directions then we have negative work and the system is losing energy to the surroundings
If force and distance are perpendicular such as centripetal force then there is NO WORK
What are the equations for power
P = W/change in time P = Fvcos
When mcat asks for rate at which work is done or energy per second what is it referring to
POWER
If a system has work added or removed and therefore doesnt equal the change in energy then what must have happened
Loss or gain of heat
