Physics Questions

The water rise in a capillary tube dipped in water is such that the weight of water in the tube above the surface of water in the vessel is equal to  the upward force due to surface tension. So it is clear that if the bore to the tube is decreased , the height of the water column in it  must be greater.

Rolling friction or rolling drag is the force resisting the motion when a body rolls on a surface. It is mainly caused by non-elastic effects, that is, not all the energy needed for deformation of the wheel, roadbed, etc... is recovered when the pressure is removed.

Another cause of rolling resistance lies in the slippage between the wheel and the surface, which dissipates energy.

Siphon is a tube bent to form two legs of unequal length by which a liquid can be transferred from a reservoir and then down to a lower level of it.

Siphon will fail to work if, the level of the liquid in the two vessels are at the same height.

Parabola, because when the coin is dropped at a particular point, it has the same velocity as the running train. So, by Newton's first law, it continues its motion horizontally with that velocity. But then, it is also pulled down by earth's gravity continuously. In this situation its horizontal motion gives way to the parabolic motion until it reaches the ground.