PHYS 1003 Lecture 9: 9. Power & PE
26 Dec 2017
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Power is the rate at which work is done or rate that energy is used in a system (since w= k) Average power p =w ( u)/ t and instantaneous power is p =dw/dt => j/s => watt (w) o o. Important to tell how long a task of transferring energy will take. Bodies convert 50% of energy into work and brain converts 20% of energy input (power x 20%) P = f v or = fvcos is the same as p = w/ t when there is constant velocity (integral of v) and average/instantaneous velocity are equal (propulsive force since fnet = zero) Potential energy and internal forces: potential energy is stored if a system changes state such as an object changes height in a gravity field and spring is compressed or stretched. o. Conservative forces and potential energy: o o o.
