Explain dynamic lift with examples.

Explanation

Dynamic lift on a spinning ball: Consider the motion of a spinning ball. Its motion consists two parts 1) Translatory motion 2) Self rotation called spinning.
1) Translatory motion: Due to translatory motion it passes through the medium air with a velocity say (v). Due to translatory motion the number of streamlines on the top of the balls and at the bottom of the ball are equal. So there is no resultant force on the ball due to translatory motion throught the fluid. Hence dynamic lift is zero.

2) For Spinning motion: Let the ball rotates about its axis with a velocity say `DeltaV` in clockwise direction since surface of ball is not perfectly smooth it with drag air molecules with it. So at the top layers the velocity of air is `V+ DeltaV` due to air drag. At bottom layers the velocity of air is `V- Delta V`.
As velocity is more at top layers pressure is less and velocity is less at bottom layers, so pressure is high at bottom layers. This is due to Bernoulli's theorem.
Due to the pressure difference at bottom layers and top layers some upward thrust will act on the ball. So some dynamic lift with act on a spinning ball. As a result the path of the spinning ball is curved.