# Cricket ball / projectile question

• sarahcate
In summary, the conversation revolves around a question regarding a cricket ball being bowled from a height of 2.3m and bouncing over stumps that are 0.71m high, 20m away from the bowler. The conversation includes different approaches to solving the question and potential mistakes made. Ultimately, the conversation concludes with the suggestion to clarify with a teacher and the mention of the harsh grading for the question.
sarahcate
I am trying to repeat a quesion I had got wrong about a cricket ball. The question is

"A cricketer bowls a ball from a height of 2.3m. The ball leaves his hand horizontally with a velocity u. After bouncing once, it just passes over the stumps at the top of its bounce. The stumps are 0.71m high and are situated 20m from where the bowler releases the ball.
a) show that from the moment it is released the ball takes about 0.7s to fall 2.3m
b) How long does it take the ball to rise 0.71m after bouncing?"

Part a I'm ok with. I used v^2 = u^2 +2ax using
a = -9.81m/s2
x = 2.3m
u = 0m/s
to find v = -6.72 m/s

i then used v = u +at
to give t = (v-u)/a = 0.68s

For part b I thought I could use a similar approach saying that at the top of it's bounce the vertical component of the velocity will be zero and the only acceleration is due to gravity. So using v^2 = u^2 +2ax
with v= 0m/s
a = -9.81m/s2
x = 0.71
I got u = 3.73 m/s

and substituing that into t =(v-u)/a, t = 0.38s
unfortunately this was wrong and I got 0 out of a possible 3 marks.

Please can anyone help me with where I am going wrong? The only thing I can think of is that there is some additional acceleration in the vertical direction (from the bounce??) but I don't know how to work this out. If you can point me in the right direction that would be brilliant.

Thank you!

Hey I’m not too sure, but wouldn’t the x value in the second vertical part be larger as it travels over the wickets, it says that it is at its max height over the wickets, so all that that is saying is that its max bounce height is 20 meters from where the ball was released

oh wait sorry I am wrong

no wait I am sort of right! lol yea u can't sub V=0 when x=0.71, because the ball travels over the wickets!

lol so X > 0.71. when V= 0.

I says it 'just' passes over the stumps at the top of its bounce so doesn't that mean the top of the bounce is at 0.71m?

yea ok maybe, lol better ask your teacher, lol i kno i would have not got that question right either! id say you would have to include 20m some how because otherwise it wouldn't have been given. lol good luck lol
lol and let me kno please!

yeh...you have to include that there is 20 m that they ball has to travel because 0.38 s for a ball to travel 20 m is far to fast...i still think it is pretty harsh that you didnt get any marks...

## What is a cricket ball?

A cricket ball is a hard, spherical object used in the sport of cricket. It is typically made of cork and covered in leather, and is approximately 22 centimeters in circumference and weighs between 155.9 and 163.0 grams.

## What is the purpose of the seam on a cricket ball?

The seam on a cricket ball is raised stitching that runs around the circumference. It plays a crucial role in the game as it allows the ball to grip and spin when bowled by a player, making it more challenging for the batsman to hit.

## How fast can a cricket ball be bowled?

The fastest recorded delivery in international cricket was bowled by Shoaib Akhtar in 2003, at a speed of 161.3 km/h (100.2 mph). However, the average speed of a professional cricket ball is around 130 km/h (80 mph).

## Why do some cricket balls swing and others don't?

Swinging in cricket is when the ball deviates from its expected path due to air pressure differences caused by the seam. This can be influenced by the ball's condition, atmospheric conditions, and the bowler's technique. The direction of the seam also plays a significant role in determining whether a ball will swing or not.

## How is a cricket ball made?

A cricket ball is typically made of cork, which is covered in layers of tightly wound string and then coated in leather. The leather is cut into two kidney-shaped pieces, which are then hand-stitched together to form the ball's outer shell. The ball is then polished and dyed to the desired color. The entire process is done by hand and requires skilled craftsmanship.

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