How do you find the initial velocity of a projectile given angle/distance?

[iamcgettigan]

Homework Statement

I am in 10th grade physics. The question is: A person standing on top of a 30.0 m high building throws a ball with an angle of 20.0° below horizontal. If the ball lands 29.3 m away from the building, what is the initial velocity of the ball? I know the answer is 16m/s, however I am unsure of how to arrive at this answer.

Relevant Equations

s=ut+½at^2

I tried resolving the information given into vertical and horizontal components. I then tried to find time, as this is how I would find the initial velocity. However, I am unsure of how to use the angle in this problem to help solve it. I am also unsure of how to find the initial velocity only given angle and distances. Any help would be greatly appreciated!

 

[haruspex]

Homework Statement:: I am in 10th grade physics. The question is: A person standing on top of a 30.0 m high building throws a ball with an angle of 20.0° below horizontal. If the ball lands 29.3 m away from the building, what is the initial velocity of the ball? I know the answer is 16m/s, however I am unsure of how to arrive at this answer.
Relevant Equations:: s=ut+½at^2

I tried resolving the information given into vertical and horizontal components. I then tried to find time, as this is how I would find the initial velocity. However, I am unsure of how to use the angle in this problem to help solve it. I am also unsure of how to find the initial velocity only given angle and distances. Any help would be greatly appreciated!

Please post your work as far as you get (and please, not as an image).

In the standard form of constant acceleration equations (SUVAT) there are five variables. Each equation relates four of them, so five equations for vertical motion. Horizontal is somewhat simpler.

The trick is to identify those variables which are of interest and choose your equations accordingly. Any variable you are given in the question and any variable you are asked to find is of interest. A variable which connects the horizontal and vertical motions (there is one here) is also relevant.

 

[iamcgettigan]

Please post your work as far as you get (and please, not as an image).

In the standard form of constant acceleration equations (SUVAT) there are five variables. Each equation relates four of them, so five equations for vertical motion. Horizontal is somewhat simpler.

The trick is to identify those variables which are of interest and choose your equations accordingly. Any variable you are given in the question and any variable you are asked to find is of interest. A variable which connects the horizontal and vertical motions (there is one here) is also relevant.

Thank you for your response. I am sorry to have somewhat wasted your time as I have figured it out. Thanks again.

 

[haruspex]

Thank you for your response. I am sorry to have somewhat wasted your time as I have figured it out. Thanks again.

That's fine - glad you got there by your own efforts.