## Dynamics/Kinetics

## Newtons 1st Law

All things at rest want to stay at rest want to stay at rest, all things in motion want to stay in motion (unless acted on by an external force). A bowler must supply the force required to bring the ball from rest to motion. The inertia of the ball will try to oppose the bowlers attempts to accelerate the ball and therefore he must provide a force that will overpower the ball's resistance. Another form of Newtons Law of Inertia is the ball being acted upon by an unbalanced force which is the bat. The ball will remain in motion unless it is acted upon by the bat. An example of this is the the bowler throwing the ball, if the ball is not intercepted by the batter or the wicket keeper(catcher) the ball will keep going. But the bat , an unbalanced force, brings the ball into play demonstrating the law of Inertia.

## Newtons 2nd Law

F = ma, force = mass times acceleration. The force required to accelerate the ball is proportional to the magnitude of the acceleration, and this proportionality constant is equal to the mass of the cricket ball. Even though the mass of a cricket ball is relatively small when compared to a human body, the running speed of a bowler in his run up is small compared to the speed of the ball when bowled, so he needs to generate the acceleration of the ball in his delivery action and apply a fairly large force providing a fairly large acceleration in a short period of time.Newtons. For cricket this means that the harder the ball is hit the farther it will go.

http://www.youtube.com/watch?v=U2YdxMabMFc -> UTV 2012

## newtons 3rd Law

**For every action, there is an equal and opposite reaction.(Newton,1686)**There are a few things that have reactions forces in cricket it stars of with the ball bouncing of the grass after being thrown, their is an reaction force from the ground to the ball. The second time there is a reaction force is when the ball makes contact with the bat the bat is providing an equal or greater reaction force to drive the ball. The third force is the force of the ball being caught to your body when the ball is caught there is a reaction force from your hands onto the ball.

ESPN 2006 --> http://www.youtube.com/watch?v=7t_sJH8jRks

## Free body diagrams of the various points of a cricket ball

## Air Resistance on a cricket ball and what it means

Air plays an important role in cricket, it causes the ball slow down through the air and it can cause a ball to curve or swing away from the path it would otherwise follow. One cubic meter of air at ground level weighs 1.21kg. A cricket ball weighs approximately 0.156kg.

The evidence above proves that in fact the air resistance does have a lot of affect on the ball, it can make the ball go slower or swing helping the bowler confuse the batsmen.

*"If you drop a cricket ball out of a helicopter hovering 300 m above the ground, it will accelerate up to 123 km/hr in about 5 seconds, having fallen through a distance of about 100 m. It will then fall the remaining 200 m to the ground at 123 km/hr, without gaining any additional speed. At 123 km/hr, the force of gravity pulling the ball down is equal to the drag force of the air pushing it upwards. The total force on the cricket ball is then zero so it falls at constant speed after the first 100 m."(USYD,2005)***.***"A ball bowled horizontally at 123 km/hr experiences a backwards horizontal drag force that is equal to the weight of the ball. At world record bowling speeds around 160 km/hr, the drag force is 1.7 times greater than the weight of the ball. Regardless of the speed of the ball when it leaves the bowler's hand, air resistance causes the ball to slow down by about 12% by the time it lands on the pitch. It slows down by another 30% or 40% when it hits the pitch, depending on the speed of the pitch and the angle of incidence. A ball bowled at 150 km/hr will arrive 0.46 s later at the batter's end, travelling at about 85 km/hr"**(USYD,2005)*The evidence above proves that in fact the air resistance does have a lot of affect on the ball, it can make the ball go slower or swing helping the bowler confuse the batsmen.