### Swing of Cricket ball : The Magnus Effect

**BALL SURFACE**
• If during the play one side of the ball roughs
up and other side remains smooth. Then swing occurs

**SWING**
• Swing is swerving of cricket ball towards left
or right as it moves through air. This
happens when ball spins about its vertical axis or because it spins about an
axis perpendicular to the seam.

•The
fast bowlers swing the ball by making the seam inclined at angle of 15° to 25°
to the direction that the ball is headed such that the smooth portion of ball
is above & in front.

•
In this way the air flows smoothly around the smooth half but it becomes
turbulent on other side as it has to flow past the seam.

•The
turbulent air is at higher velocity. Therefore according to Bernoulli’s theorem
the pressure on these side (rough) decreases than on smooth flowing air
therefore the ball gets pushed sideways.

•This
is also the Magnus effect. This sideway swing force is maximum when speed of
ball is around 100 km/hr. But it speed of ball increases.

The reverse swing
occurs because the flow of air over smooth surface becomes turbulent. The effect can occur at low speeds if rough
end side is put forward

•

__Other factors__: affecting swing are the__atmospheric pressure__: - Due to evaporation of ground moisture. The water vapor content of air over pitch increases. This increases the partial pressure and thereby air pressure therefore as match progress the fast bowlers will be able to get more swing if they manage roughness/shine factor well.__OUTSWING__

•

__Holding the ball for an out swinger with shiny/wet side on right side__

• The ball initially moves out in the air and
comes back to the batsman sharply.
Usually, a batsman can be out by leg before as the tends to play along
wrong line.

•

__Holding the ball for an in swinger, with shiny side on the left side__
• The ball initially moves towards the batsman
and at last moment darts away from the batsman. A batsman can be caught behind
the wickets and sometimes bowled.

__STREAMLINE AND TURBULENT FLOW__

Streamline flow of a liquid is that flow in which every particle of the
liquid follows exactly the path of its preceding particle and has the same
velocity in magnitude and direction as that of its preceding particle while
crossing through that point.

• When a liquid moves with a velocity greater than its
critical velocity, the motion the
particles of liquid becomes disorderly or irregular. Such a flow is called turbulent flow.

__Curved motion of spinning ball (Magnus effect)__

• When a spinning ball is thrown, it deviates
from its usual path in flight. This is due to magnus effect..

• If the ball is spinning as well as moving
linearly, the streamlines at the top of ball due to two types of motion are
opposed to each other and those below are in the same direction. As a result of
it, the velocity of air flow is greater below than above the ball. Now, according to Bernoulli’s principle, the
pressure on the upper side of the ball becomes more than the pressure on the
lower side of ball. Due to it, a resultant force F acts upon the ball at right
angle to the linear motion in the downward direction, resulting the ball to
move along a curved path. This dynamic force due to spinning of ball is called

__Magnus effect__.
Hope this post is helpful ....

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