Energy, Work and Power
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what is kinetic energy associated with?
moving or vibrating objects
what is gravitational potential energy associated with?
position or height of an object
what is elastic potential energy associated with?
stretched (or compressed) object
what is chemical potential energy associated with?
battery, food, fossil fuel
what is thermal energy associated with?
temperature of an object
what is light energy associated with?
light
what is electrical energy associated with?
position and motion of electric charges
what is nuclear energy associated with?
nuclear reactions (fission and fusion)
what does principle of conservation of energy mean?
energy cannot be created nor destroyed, but can be converted from one form to another. the total energy in an isolated system is constant.
what is the real world application of principle of conservation of energy?
energy supplied (work done) and energy lost (friction and resistance, light or sound)
how do we apply principle of conservation of energy in mathematical form?
sum of internal energies in the system + work done to the system = sum of final energies in the system + energy lost from the system
what is work done?
Work done by a constant force on an object is given by the product of the force and the distance moved by the object in the direction of the force.
how do we calculate the work done?
W (work done in J)=F (constant force in N) x s (distance moved in direction of force in m)
define kinetic energy
energy of a body due to its motion
how do we calculate kinetic energy?
KE (in J)= m (mass in kg) x v (speed of object in m/s)
define gravitational potential energy
energy a body has due to its position above the ground
how do we calculate GPE?
GPE (in J)= m (mass in kg) x g (gfs in N/kg or acceleration due to gravity in m/s^2) x h (height of object above ground in m)
what is the relation between GPE and KE?
by principle of conservation of energy, all initial GPE will be converted to KE just before touching the ground. assumption is that there is no energy loss to surroundings. gain in KE=loss in GPE
what is power?
the rate of work done, rate of energy conversion
how to calculate power?
P (power in W)= W (work done in J)/ t (time in s) = E (energy converted in J)/t