Q.1. Explain why
The angle of contact of mercury with glass is obtuse, while that of water with glass is
acute.
ANS- The angle between the tangent to the liquid surface at the point of contact and the surface
inside the liquid is called the angle of contact (θ), as shown in the given figure
(USE TEXT)
Q.2. A drop of liquid under no external forces is always spherical in shape?
ANS-A liquid tends to acquire the minimum surface area because of the presence of surface
tension. The surface area of a sphere is the minimum for a given volum
external forces, liquid drops always take spherical shape.
Q.3.Water on a clean glass surface tends to spread out while mercury on the same surface
tends to form drops ?
ANS-Mercury molecules have a strong force of attraction between themselves and a weak force of attraction toward tend to form drops. On the other hand, water molecules make acute angles with glass. They have a weak force of attraction between themselves and a strong force of attraction toward solids.
Q.4.A spinning cricket ball in air does not follow a parabolic trajectory -EXPLAIN WHY ?
ANS-A spinning cricket ball has two simultaneous motions
types of motion oppose the effect of each other. This decreases the velocity of air flowing
below the ball. Hence, the pressure on the upper side of the ball becomes lesser than that
on the lower side. An upward force acts upon the ball. Therefore, the ball takes a curved
path. It does not follow a parabolic path.
Q.5.What is a streamline flow ?
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