Question of Physics

Question

A block of mass m is placed on an inclined plane of mass M. The block is released from rest at an initial height h. All the surfaces are frictionless. In which direction (x or y) the momentum of the system is conserved? Determine the velocities of the inclined plane and the block (g is the gravitational acceleration.).

Answer 1

Hi Hasan T.,

Let's take the items requested in the order suggested. Is there any external force acting in the x-direction? NO! Is there any external force acting in the y-direction: YES! (gravity, also the support of the table). So: the block must acquire kinetic energy equal to its initial potential energy E=mgh = (1/2)mv^2 . The momentum in the x-direction is conserved, hence Mv(plane) = -mv(block, final)^2 . Velocities are measured vs. the frame of the table.

You should be able to take it from there?

Since frictional force is proportional to applied load (in normal kinds of conditions), you might ponder what happens to an automobile barely adhering on a slippery slope if you jack it up to change a flat tire.

-- Cheers, -- Mr. d.