7. 2 points OSColPhys2016 7.2.WA.009 My Notes Ask Your Teacher An athlete with a

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7. 2 points OSColPhys2016 7.2.WA.009 My Notes Ask Your Teacher An athlete with a mass of 64.5 kg is in a cross country race, and at one instant he has a speed of 5.10 m/s. (a) What is his kinetic energy at this instant? KEi = (b) If he wishes to doubles his speed to reach the finish line, his kinetic energy will change by what factor? KEr KE Additional Materials Reading 8. -2 points OSColPhys2016 7.2.WA.010 My Notes Ask Your Teacher A 0.44-kg object travels from point A to point B. If the speed of the object at point A is 3.0 m/s and the kinetic energy at point B is 8.0 J, determine the following. (a) kinetic energy of the object at point A (b) speed of the object at point B m/s Additional Materials Reading

Explanation / Answer

7] KE= 0.5mv^2 = 0.5*64.5*5.1^2 =  838.82 J

KEf/KEi = Vf^2/Vi^2 = [2]^2 = 4

8] KE at A = 0.5mvA^2 = 0.5*0.44*3^2 = 1.98 J

speed at B = sqrt(2KE/m) = sqrt(2*8/0.44) =  6.03 m/s

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