State what is meant by centripetal acceleration.
An unpowered toy car moves freely along a smooth track that is initially horizontal. The track contains a vertical circular loop around which the car travels, as shown in the figure below.
The mass of the car is 
and the diameter of the loop is 
. Assume that the resistive forces acting on the car are negligible.
State what happens to the magnitude of the centripetal acceleration of the car as it moves around the loop from X to Y.
Explain, if the car remains in contact with the track, why the centripetal acceleration of the car at point Y must be greater than 
.
.
