Work Have you done any work today Work

Work Have you done any work today? • Work: (W) the transfer of energy that occurs when a force makes an object move. – Measured in Joules – Two conditions must be met: • Object must move • Force must be applied in the direction of the movement.

Work Can be summarized as an equation. W = Fd W = work F = force d = distance Measured in J Measured in N Measured in m Example #1: You move a 75 kg refrigerator 35 m. This requires a force of 90 N. How much work, in joules, was done while moving the refrigerator? m = 75 kg d = 35 m F = 90 N W=? W = Fd W = (90)(35) W = 3, 150 J

Practice Time 1. A book weighing 1 N is lifted 2 m. How much work was done? Answer: W = 2 J 2. A 1 kg book is lifted 2 m. How much work was done? Answer: W = 19. 6 J 3. 250 J of work are needed to push a box up a ramp. The force needed to push the box up the ramp is 10 N. How far up the ramp was the box pushed? Answer: d = 25 m 4. If 56 J of work energy is required to lift a dumbbell to a height of 7 m, what is the weight of the dumbbell? Answer: w = F = 8 N

Power • Power: (P) the amount of work done in a certain time; the rate at which work is done. P=W t P = power W = work t = time Measured in J/s Or Watts = W Measured in J Measured in s

Example #2 It took 150 seconds to move a refrigerator. You did 3, 150 joules of work in the process. How much power was required to move the refrigerator? t = 150 s W = 3, 150 J P=? P=W t P = 3150 P = 21 J/s or 21 Watts