graviyt/maths question

[CBORDINO]

Hi guys, I have another question, this one is really hard!!!

A woman throws a cricket ball vertically upwards into the air. The ball leaves the woman’s hand 1.8 m above the ground, with a speed of 9.7 m s−1. It rises and then falls back to the ground. By considering the energies involved, calculate the ball’s speed at the point at which it hits the ground.

You may assume that the acceleration due to gravity, g, is 9.8 m s−2 and you may neglect air resistance.

 

[coyote]

how big are a cricket's balls, anyway?

 

[CBORDINO]

Re: gravity/maths question

I never thought of it that way

 

[kihira]

I think someone else had this same question? and maybe it was answered?

edit: see here
http://www.socialphobiaworld.com/can-anyone-help-with-physics-assignment-30720/#post385707

 

[divethruhaze]

Got 11.37 m/s as answer.

Used the kinematics equation:
v^2 = u^2 + 2as

v=final velocity
u=initial velocity
a=acceleration due to gravity
s=displacement from start

Took upward direction to be positive. Therefore the values:
v= to be found
u= 9.7
a= -9.8
s= -1.8

v^2 = (9.7)^2 + (2)*(-9.8)*(-1.8)
v^2 = 129.37
v = 11.37

 

[CBORDINO]

I asked a tutor and he got the same answer, thank you very much