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Find magnitude of force to this simple Physics Friction problem?

A 40-kg box is moving on the floor. The coefficient of static friction between the box and the floor is

0.650, and the coefficient of kinetic friction is 0.500. If the pulling force is applied horizontally, what is

the magnitude of the force to maintain a constant velocity motion?

2 Answers

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  • Because we are finding the force to maintain motion, we can ignore the static friction coefficient. When dealing with friction,

    Force = (Coef. Frict.)*(normal force)

    Since the box is on a horizontal surface, and the force applied is also horizontal, our normal force is the same as the weight. To find weight,

    Force = mass*acceleration

    In this case, our acceleration is that of gravity, 9.81m/s^2

    Force = (40kg)*(9.81m/s^2)

    Force = 392.4 N

    This is the normal force

    We then plug this into our friction equation.

    Force = (.500)*(392.4N)

    Force = 196.2N

  • 6 years ago

    Use the kinetic friction 0.5 For constant velocity, Fnet = 0 = 40*g*0.5 - F => F = 196N

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