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## Homework Statement

Johnny, of mass 65 kg, and Lucy, of mass 45 kg, are facing each other on roller blades. The coefficient of kinetic friction between the roller blades and concrete surface is 0.20. When Johnny pushes Lucy from rest he applies a force for 1.0 s. Lucy then slows down to a stop in another 8.0 s. Calculate:

a. The applied force exerted by Johnny on Lucy. [790 N]

b. How long it takes Johnny to come to rest. [5.1s]

## Homework Equations

F = ma

Vf = Vi + at

x(t) = Vi * t + 0.5*a*t^2

## The Attempt at a Solution

Fk = (miu)*mass*9.81 = (0.2) (45Kg) (9.81 m/s^2) = 88.3 N

Vf = Vi + at = 0 + a(8s)