Physics

To find the coefficient of kinetic friction () between the sofa and the floor, we can use the following information:

 

1. Weight of the sofa: 400 N (this is also the normal force since it's resting on a horizontal surface).

2. Force required to start moving the sofa: 50 N (this is less than the maximum static friction, so the sofa does not move).

3. Force required to keep the sofa moving at constant speed: 140 N (this equals the kinetic friction force since it's moving at constant speed).

 

Calculate the Kinetic Friction Force

The kinetic frictional force () is equal to the force required to keep the sofa moving at a constant speed:

 

Calculate the Coefficient of Kinetic Friction

The formula for kinetic friction is:

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