- #1
freshcoast
- 185
- 1
Homework Statement
A 25kg box of books is pushed up a ramp and into the back of a pickup truck. The box-ramp system has coefficients of friction (static = 0.6, kinetic = 0.45). The ramp is placed at the maximum angle possible with respect toe the horizontal before the stationary box would slip down the ramp. Under these conditions:
a)What is the magnitude of the maximum possible static friction force?
b)An external force parallel to the floor is now applied to the box. What minimum force must be applied tot he box to cause it to begin to move up the ramp?
c)What minimum force must be applied to cause it to continue to move up the ramp with constant speed?
Homework Equations
ƩF = ma
The Attempt at a Solution
For part a) I drew a free body diagram of the box and summed all the forces in the +I direction and made it equal to 0 since we are dealing with a static friction. And in the J direction I summed all the forces, made it equal to 0 since object is not moving up or down, and from there I was able to find the normal force and substituted that into the friction force to find the angle.
For part b) I drew a free body diagram, summed the forces in I and J directions but added a new unknown force in the I direction and used the coefficient of the kinetic friction force to get the minimum force needed for the box to begin to move. I also used the same angle found in part a) since the ramp is placed at the maximum possible angle before the box slips
Please check to see if I was able to do parts a) and b) correctly,
Now I am having trouble with part c, for the box to continue to move up with a constant speed, would that mean there would be no force to slow it down such as the friction force moving in the opposite direction?
Thanks again for your input