Transferring Energy Work and Heat

We define work, w, as the energy transferred when a. force moves an object. A force is any push or puU exerted on an object. The magnitude of the work equals the product of the force, F, and the distance, d, the object moves  

We perform work, for example, when we lift an object against the force of gravity. If we define the object as the system, then we—as part of the surroundings—are performing work on that system, transferring energy to it. 

Plan We can calculate the work done in lifting the ball by using Equation 5.3 w = F X d. The kinetic energy of the ball just before it hits the ground equals its initial potential energy. We can use the kinetic energy and Equation 5.1 to calculate the speed, v, just before impact. 

the bowler has done 85 J of work to lift the ball to a height of 1.6 m. 

Check Work must be done in (b) to increase the potential energy of the ball, which is in accord with our etqjerience. The units are appropriate in (b) and (c). The work is in units of J and the speed in units of m/s. In (c) we carry an additional digit in the intermediate calculation involving the square root, but we report the final value to only two significant figures, as appropriate. 

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