posted by Mischa on .
A student pulls on a rope attached to a box of books with a mass of 35.0 kg and moves the box up a ramp at 12 degrees with the horizontal. If the box starts from rest at the bottom of the ramp and is pulled at an angle 25.0 degrees with respect to the inclince and with a 185 N force, what is the acceleration up the ramp? Assume Mu,k= .27.
You have two component of the pulling force on the box. 185sinTheta is pulling normal to the plane, reducing the normal force (mgcos12) to a new normal force mgcos12 - 185sin25. This makes the force of friction mu(mgcos12 - 185sin25)
Of course, some of the book weight is down the plane...mg*sin12
The other componetn of the pullng force is up the ramp...185cos25
Net force= mass*acceleration
185cos25-mu(mgcos12 - 185sin25)-mg*sin12= mass*acceleration
solve for acceleration.
check my thinking.
sorry but can you please help me seriously...