# Coefficient of friction, momentum, speed and distance

I have some physics questions:

1. It takes a force of 300 N to keep a 500-N box sliding across a floor. What is the coefficient of the sliding friction?

2. A force acting on a 5.0-kg body increases its speed uniformly from 2.0m/s to 8.0m/s in 3 s. What is the initial momentum of the body? What is the final momentum of the body? What is the force acting on it?

3. In order to swing a .1kg mass tied to one end of a cord in a horizontal circle of radius .5 m so that its tangential speed is .2m/s what centripetal force must you exert on the mass through the cord?

4. At what distance from the center of the earth does g = 2.0 m/s x s (s squared)

https://brainmass.com/physics/solar-system/coefficient-friction-momentum-speed-distance-521259

#### Solution Preview

If 300N is the minimum force required to keep an object from moving, then it is also the maximum amount of force caused by friction. As a result, we can say that:

Force of friction = coefficient of friction x normal force of object = 300N

Ff = uN = 300

The normal force, assuming that the object is sitting flatly on a surface, is exactly equal to that of the force of gravity. This is because gravity on a still object causes the object to push down onto the surface where it rests, and there is an equal and opposite force - the normal force from the surface. We know the object is 500N in weight, and thus, again if sitting flatly, so ...

#### Solution Summary

Coefficient of friction, momentum, speed and distance are examined.