Power Average power: aveWPt=ΔInstantaneous power: tdWPFdtFυυ===iGGP= F υif force and velocity have the same direction, P= −F υif they have opposite directions. Example The 5 Kg cart slides up the frictionless 30°ramp under the action of a horizontally applied force Fas shown. The cart starts from rest and moves with a constant acceleration of 0.5 m/s2from Ato B. Find the average power by Ffor the motion from Ato B. Find the instantaneous power of Fwhen the cart reaches point B. (Ans: Pave= 27 W, PB= 54 W) 4 m F A B Work-kinetic energy equation 211 2211 2112KWKmWm222υυ−−+=⇒+=: Motion of the body is from position 1 to position 2
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