# Kinetic force

1. Aug 5, 2015

### Dalip Saini

1. The problem statement, all variables and given/known data
A crate on a rough horizontal floor is being moved horizontally by a force applied at a 16 degree angle above the horizontal. This is the smallest force that will move the crate at constant speed. What is the coefficient of kinetic friction?

• A :

.11

• B :

.27

• C :

.96

• D :

It depends on the size of the force.

• E :

.29

2. Relevant equations
friction force = (coefficient of kinetic friction) (normal force)

3. The attempt at a solution
I am really confused on how to solve this problem without the magnitude of force applied or the weight of the crate.

2. Aug 5, 2015

### tommyxu3

You could decompose the force and analyze if the information is enough for you to solve the problem. Maybe you should have a graph and try to list their relation first and conclude?

3. Aug 6, 2015

### haruspex

I recommend trusting the question. Put in unknowns (m, F, ...) as necessary and expect them to disappear later in the algebra.
Often you can predict that they will. In the present case, if you double the mass then quite clearly you can correspondingly double the force. If the crate moves with one set of values it will move with the other set. The value of g can't matter either.