Projectile motion of tennis ball

[kisha]

Homework Statement

A tennis player serves in a match.He hits the tennis ball so that it flies off the racket with a velocity of 50m/s at 10° to the horizontal.

Sx=11m
Sy=2.4 - 1.07 = 1.33m
ux=50cos10°
uy=50sin10°
time=?

a)Show that the ball cannot pass over the net.

b)The player serves again.He hits the ball at the same height.The ball flies off at the same speed but it only makes an angle of 5° with the horizontal.

(i)Show that the ball passes over the net this time.
(ii)When does the ball land after the serve?Find its horizontal displacement when it lands.
(iii)Find the velocity at which the ball hits the floor.

Homework Equations

Vy = Uy - gt
Sy=Uy - 1/2gt^2
Sx=Ux(t)
Vx=Ux

The Attempt at a Solution

Time of flight=[PLAIN]http://img600.imageshack.us/img600/5889/29072134.png

vertical distance = h = usinθ(t)-1/2gt^2
=[PLAIN]http://img825.imageshack.us/img825/369/24954548.png
=[PLAIN]http://img202.imageshack.us/img202/5079/78644637.png

Since,
Sy=Sxtanθ

h=[PLAIN]http://img191.imageshack.us/img191/6696/36239012.png

Therefore,the ball passes below the net at a separation of=

[PLAIN]http://img576.imageshack.us/img576/6231/89145724.png

In other words,it is impossible for the ball pass the net.

Can anyone help with this?How to prove the ball cannot pass over the net?

 

[1994Bhaskar]

can you explain more?
IS THE PLAYER DOING A TENNIS SERVE OR BADMINTON SERVE ,i.e. IS HE SWINGING HAND FROM ABOVE HEAD OR BELOW STOMACH?

 

[kisha]

re 1994Bhaskar:

The player swinging his hand above head:).

 

[xiaoB]

" Sy=2.4 - 1.07 = 1.33m "

Can you tell me is it 2.4m is the player height and the 1.33m is the net height ?:shy:

If not going wrong! Your distance vertical = h , should be S_y then you can get the answer.

 

[kisha]

re xiaoB:

Yes:).you're right

 

[xiaoB]

re xiaoB:

Yes:).you're right

If not going wrong! Your distance vertical = h , should be S_y then you can get the answer.

 

[xiaoB]

If not going wrong! You can poof the h =0.7...m is below then the net height.:shy:

 

[kisha]

can you explain more?
IS THE PLAYER DOING A TENNIS SERVE OR BADMINTON SERVE ,i.e. IS HE SWINGING HAND FROM ABOVE HEAD OR BELOW STOMACH?

If not going wrong! You can poof the h =0.7...m is below then the net height.:shy:

I guess it!thank you for your help:).You get me out of trouble.