tennis ball example/coefficient of restitution

a tennis ball is hit from a height h above the ground with a speed V and at an angle alpha to the horizontal. it hits a wall at a horizontal distance d away . Air resistance is negligible

i was told to find expressions for the height and velocity of the ball for which i did shown below

Vx = Vo*cos(alpha)

Where :

Vo is the initial velocity

alpha is the launch angle

Vx is the x component of velocity

Vy = Voy*sin(alpha) - g*t

From the pythagorean theorem V = sqrt(Vx^2+Vy^2)

X = Vo*cos(alpha)*t

Y = Vo*sin(alpha)*t - 1/2*g*t^2

Assuming that i started at (x,y) = (0,0) i will then end upat the point (D,h)

that was the first part of the quesiton...but the part im stuck on is ...auusuming that the coefficient of restitution between the tennis ball and the wall is e, i need to write down an expression for te the velocity of the ball immediately after impact......is there anyone that can help ???thankz

expression/coefficient of restittuon

Quote:

Originally Posted by **malaygoel**

I think it will end up at (D,-h).

Let $\displaystyle t_1$ be the total time of flight.

You can use your equation:Y = Vo*sin(alpha)*t - 1/2*g*t^2

If t=$\displaystyle t_1$, then Y=-h.

Rest you can do yourself.

Keep Smiling

Malay

i dont understand how that will help me to find an expression for the velocity of the ball immediately after the impact, when the coefficient of restitution between the ball and the wass is e.????

thankz