What is the Initial Speed of a Baseball Thrown at a 45° Angle?

[Ki-nana18]

Homework Statement

A baseball player throws a ball a distance of 250 ft. If the ball is released at an angle of 45°with the horizontal, find its initial speed.

Homework Equations

The Attempt at a Solution

I don't know where to begin. All i know is that speed is the norm of velocity. Help?

 

[SammyS]

Suppose the initial speed is v₀. What are the vertical & horizontal components of the velocity.

 

[Ki-nana18]

x=(v₀cos 45°)t
y=(v₀sin 45°)t

 

[minifigmaster]

close. You forgot that the y equation has acceleration due to gravity, so that's \frac{-9.8}{2}t^{2}.

And is that how I'm supposed to do math equations here? Cuz I am relatively new (I signed up earlier, I just never used it till now).

 

[Ki-nana18]

Yeah, that's how you do it. And thank you. I should use (32/2)t² since the unit is feet. Correct?

 

[minifigmaster]

oh yeah, sorry but that, but glad I could help.

 

[Ki-nana18]

So what do i do next? Differentiate?

 

[minifigmaster]

oh i thought you got it. Sorry. You know that x displacement is 250 ft, and y displacement is 0. If you plug that in, you'll find you have a system of two equations with two variables--initial velocity and time. I'm sure you can solve from there.

 

[Ki-nana18]

Thank you so much!