BIO Animal Energy.? Adult cheetahs, the fastest of the great cats, have a mass of about 70 kg and have been clocked to run at up to 72 mi/h (32 m/s). (a) How many joules of kinetic energy does such a swift cheetah have? (b) By what factor would its kinetic energy change if its speed were doubled?

Solution 13E Introduction We have to calculate the kinetic energy of the cheetah using the given mass and velocity. We will then calculate the kinetic energy if the velocity is doubled and the compare the kinetic energy with the initial kinetic energy. Step 1 The kinetic energy of an object having mass m and moving with speed v is given by E = mv . 2 k 2 Now in this case we know that m = 70 kg v = 32 m/s Hence the kinetic energy is 1 2 4 E k (72 kg)(32 m/s) = 3.584 × 10 J 4 So the kinetic energy of the cheetah is 3.584 × 10 J.