theCandyman said:
Can I have some tips on where to start this problem? I have no work because I can see no work to do.
"A wooden box is placed on the left end of a 3.60-m long plywood ramp. The left end of the ramp is raised until the box begins to slide. What is the magnitude of the acceleration of the box after it starts to move?"
This is all the information. I have no way to find the coefficent of friction, no angle, and no mass for the box.
The answer is: acceleration = 0.
However, that answer assumes something that isn't given in the problem, and it can make it rather complicated.
When you increase the angle of the ramp, the weight along the inclined will start pulling the box down. Now, the problem here is that typically, the
static friction tends to be larger than the
kinetic friction. In answering your question, I have made the allowance that as you increase the angle of the ramp, you continue to give the box a slight push. The box will move and then stop when the ramp angle is small, but at a particular angle, it will then start to move with constant velocity. It means that at this angle, the frictional force is exactly equal the the component of the weight along the incline, so they balance out. So acceleration is zero.
If you do not give it a slight push, the object will remain stationary, and remains stationary
beyond this angle because of what I said about static friction above. By the time it moves, it will be accelerating because the component of the weight along the incline will definitely be larger than the frictional force. If this occurs, or if this is what is really being asked in your problem, then your problem cannot be answered because it requires explicit knowledge of the ratio of the coefficient of static friction to the kinetic friction.
Zz.
