Kinematics Projective Motion Problem

[physics7889]

Projectile Motion

Homework Statement

Joe Carter hit a fly ball during spring training. It just cleared a 10m fence, Calculate the speed of the ball when it leaves his bat at ground level. Ignore friction.
http://img155.imageshack.us/img155/7161/physics.png [Broken]

Homework Equations

The Attempt at a Solution

v in x direction was found to equal 12.5 m/s which is the same as v in y direction since the tangent formed was a 45-45-90 degree angle triangle.

 

[nickjer]

You need to show your work, along with relevant equations. Also, what is the 8 m? Is that the distance from the batter to the wall, or the distance from the landing spot to the wall?

 

[physics7889]

its the distance from the fence to the landing point of the projectile

 

[nickjer]

Is the 45 degree angle given to you, or something you solved for?

 

[physics7889]

It was given to me, this is really all the information that was given

 

[nickjer]

Well it looks like your attempt at the solution is right so far. But it is recommended you show your work, so it doesn't look like you just copied the answer from somewhere.

Also, what do you know about the velocity in the x-direction since the only acceleration is the gravitational acceleration in the y-direction.

 

[rl.bhat]

When the ball reaches the ground, vx remains the same.
vyf^2 = vyi^2 + 2*g*h.
vyi is the same as vx, which you have found. h is given. Find vyf.
Initial velocity v = sqrt(vyf^2 + vx^2)