Question

When a board with a box on it is slowly tilted to a larger and larger angle, common experience shows that the box will at some point "break loose" and start to accelerate down the board. The box begins to slide once the component of its weight parallel to the board, w||, equals the maximum force of static friction. Which of the following is the most general explanation for why the box accelerates down the board after it begins to slide (rather than sliding with constant speed)?

Answer 1

The coefficient of kinetic friction is less than the coefficient of static friction.

Step-by-step explanation:

At the point when the box finally does "break loose," the component of the box's weight that is parallel to the board, w|| , is equal to μsn (the maximum force of static friction). For the box to then accelerate, there must be a nonzero net force acting on the box parallel to the board. In other words, w|| must be greater than the force of kinetic friction, fk=μkn . Therefore the force of kinetic friction, μkn , must be less than the force of static friction, μsn , which implies μk<μs , as expected.

Answer 2

friction and inertia is acting upon the box