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Question 6.1: Calculating Kinetic Energy A good pitcher can throw a baseba...

Calculating Kinetic Energy

A good pitcher can throw a baseball so that it travels between 60 and 80 miles per hour. A regulation baseball weighing 143 g (0.143 kg) travels 75 miles per hour (33.5 m/s). What is the kinetic energy of this baseball in joules? in calories?

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You substitute into the formula E_k  = \frac{1}{2} m v^2 using SI units.

E_k  =  \frac{1}{2} \times 0.143  kg \times(33.5  m / s )^2  =  80.2  J

Using the conversion factor 1 cal/4.184 J we obtain

80.2  \cancel J  \times \frac{1  cal }{4.184  \cancel J}= 1 9 . 2  cal

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