Question

Consider a toy car on a track. Say the track is not leveled and we attempt to level the track such that `theta=0` (See image). In an ideal physics set up, even a very small angle should create an acceleration. So, why does the car still not move?

Answer 1

This can be explained nicely by resolving the forces acting on the toy car on an inclined plane.

It is the downward component of its weight i.e `mg sin theta` which creates the downward motion of the toy,which gets balanced by `mumgcos theta` i.e the frictional force acting against the direction of its motion. (`mu` is the coefficient of frictional force)

So,net movement of the toy will be only when, `mg sin theta > mumgcos theta`

Now,we know for smaller values of `theta`, `cos theta>sin theta`

Now,multiplying `cos theta` with `mu` will not affect the `cos theta` much until and unless the surface of the inclined track is slippery i.e `mu` has very small value.

As a result large amount of frictional force manages to cancel out the downward motion of the toy,and it doesn't move.