12 Physics - Energy
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State 1o types of energy
nuclear* kinetic chemical gravitational potential geothermal* thermal light (radiated) sound electrical elastic (stain)
what are the units of energy?
Joules (J)
what are the 2 main categories of energy an object can have?
energy in action energy store
what type of energy does a moving object have?
kinetic
what type of energy would be found in a car that is stationary at the top of a hill?
gravitational potential chemical (if the car has fuel in it)
what is work?
it is the force applied to an object to make it move a given distance
what is the unit of work?
Joules (J)
what is the equation for work done?
work done (J) = force (N) x distance
what is the equation for force?
force = mass (Kg) x acceleration (m/s^2)
what is the value for acceleration due to gravity?
10 N unless stated otherwise
a bag of 7 Kg is lifted onto your shoulder which is 1.5m high how much work have you done?
f = mass x acceleration f = 7 x 9.8 f = 68.6 J w = f x d w = 68.8 x 1.5 w = 102.9 J
James Bond falls out of a plane which is 30km high, he weights 75kg what work was done to j. bond?
f = 75 x 9.8 f = 735 J w = 735 x 30000 w = 22 050 000 J = 22 050 KJ
state the principle of energy conservation
energy cannot be created or destroyed, it can only be transferred from one form to another
why is a machine never 100 % efficient?
because heat energy is lost when energy is transformed, heat is always produced
a car moves due to a reaction in the engine that provides force state all energy changes from petrol to the car parked at the top of a hill
the car starts with chemical energy stored in petrol combustion happens and heat is produced -sound, heat–> energy that is wasted the car moves - kinetic energy the car parks - gravitational potential
what is GPE?
gravitational potential energy the amount of stored energy an object has based on the mass of an object, its height off the ground, and the amount of gravity it is also the amount of work an object can do due to gravity
what is the equation for GPE
GPE (J) = mass (Kg) x gravitational force (N/KG) x height (m) GPE = mgh
what is KE?
kinetic energy energy associated with a moving object it is dependent on the mass of the object and its velocity (speed in a given direction)
equation for KE
KE = 0.5 x mass x speed^2
what is the relationship between work done, GPE, and KE?
they are the same work done = GPE = KE
what is power dependent on?
work done time
what is the unit of power
Watts (W) or J/s (joules per second)
equation for power?
work done (J) or energy transformed _________________________________ time (s)
equation for acceleration?
final velocity - initial velocity ______________________ time