Projectiles launched at an angle not sure if i posted this already?

[aly1201]

Homework Statement

A diver pushes off horizontally from a cliff 35 m above the water, and they must clear rocks that extend 5 m from the base of the cliff. (a)What minimum pushoff speed is necessary to clear the rocks? (b)How long are they in the air?

Homework Equations

for (b) t=square root of 35/4.9=2.67 s I understand how to derive the time equation.
for (b) y=v(y direction)t+1/2at^2 x=v(x direction)t

The Attempt at a Solution

I solved time already, and I got 1.85 m/s for the initial velocity in the x direction, but I can't get the correct initial velocity in the y direction. I am not even sure what I am doing wrong but its frustrating.

 

[aly1201]

thats actually not projectiles launched at an angle its horizontal projectile motion sorry-I was looking at an angled problem also, which I could use help with too.

 

[hage567]

Homework Statement

A diver pushes off horizontally from a cliff 35 m above the water, and they must clear rocks that extend 5 m from the base of the cliff. (a)What minimum pushoff speed is necessary to clear the rocks? (b)How long are they in the air?

Homework Equations

for (b) t=square root of 35/4.9=2.67 s I understand how to derive the time equation.
for (b) y=v(y direction)t+1/2at^2 x=v(x direction)t

The Attempt at a Solution

I solved time already, and I got 1.85 m/s for the initial velocity in the x direction, but I can't get the correct initial velocity in the y direction. I am not even sure what I am doing wrong but its frustrating.

The initial y velocity is "given" in the problem. It is zero, since he pushes off horizontally.

 

[aly1201]

Oh ok, so I don't even have to solve for that. So the answer is really the initial velocity in the x direction? 1.85 m/s?

 

[hage567]

Yes.

 

[aly1201]

Ok thanks!