# Projectile's launch speed?

#### kcalhoun

1. Homework Statement

The highest barrier that a projectile can clear is 15.0 m, when the projectile is launched at an angle of 13.0° above the horizontal. What is the projectile's launch speed?
2. Homework Equations
kinematics equations

3. The Attempt at a Solution

delta y=15m v0x= vcos13
ay=-9.8m/s^2 ax=0m/s^2

im not sure how to use the information that i have to solve the problem

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#### LowlyPion

Homework Helper
What does clearing a maximum height barrier suggest?

Will that be the highest point of its trajectory?

#### kcalhoun

yes 15m is the highest point i just don't know how to use that to solve the problem

#### LowlyPion

Homework Helper
yes 15m is the highest point i just don't know how to use that to solve the problem
What will the vertical component of velocity need to be if it is only to go 15 m high?

vsin13?

#### LowlyPion

Homework Helper
Yes it will equal that.

But they ask you to find Vo to begin with.

#### kcalhoun

i don't know how to find Vo with the given info.. thats my problem

Homework Helper

#### kcalhoun

so use v^2=Vo^2+2aX?? But i still dont know what v or Vo are or how to get them...

#### LowlyPion

Homework Helper
so use v^2=Vo^2+2aX?? But i still dont know what v or Vo are or how to get them...
So at max height, what will the vertical velocity be again?

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