Question

A baseball player slides to a stop on level ground. Using energy considerations, calculate the distance the 50-kg baseball player slides, given that his initial speed is 5.5 m/s and the force of friction against him is a constant 550 N

  d = units =

Answer 1

Using energy conservations:

KEi + PEi + Wf = KEf + PEf

KEi = Initial kinetic energy = 0.5*m*Vi^2 = 0.5*50*5.5^2 = 756.25 J

KEf = final kinetic energy = 0, since final speed is zero

PEi = PEf = 0, Since player is at same level and on the ground

Wf = Work-done by friction = -Ff*d

Ff = Force due to friction

d = displacement due to friction = ?

Work-done due to friction force is negative because force due to friction is in opposite direction of displacement. So

KEi + 0 + Wf = 0 + 0

KEi = -Wf

KEi = Ff*d

d = KEi/Ff

d = 756.25/550

d = 1.375 m

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