Friction Questions – Coefficients of Friction and F = ma

 

Static Friction    f_{s =} U_sFn              Kinetic Friction   f_{k =} U_kFn

(force to start object moving)

Horizontal surface     f_{s = Us w}            f_{k = Uk w       AND   w = mg}

 

Ex 1) A 1000 N car skids on a wet concrete road. If the road is horizontal, what is the friction force on the car?

 

 

 

 

 

 

 

Ex 2) A skier is being pulled along a horizontal surface at constant speed with a force of 50 N. What is the weight of the skier?

 

 

           

 

 

 

 

Ex 3) A 10 kg block of wood sliding on a horizontal wooden table is brought to rest. What is the force on the block of wood that caused it to stop?

 

 

 

 

 

Ex 4) A 53 kg piece of copper is at rest on a horizontal steel table. A force is

         applied to the box and it achieves an acceleration of 0.1 m/s².  What

         is the weight of the piece of copper?