# How to find Final Speed.

1. Nov 5, 2013

### rqu1ntana

A steel ball is launched at 25 degrees above horizontal from the top of a platform that is 15 meters above ground. If the initial speed is 10m/sec, what is the final speed when it strikes the ground?

2. Nov 5, 2013

### tiny-tim

hi rqu1ntana! welcome to pf!

show us what you've tried and where you're stuck, and then we'll know how to help!

(use the standard constant acceleration equations, in the x and y directions separately)

3. Nov 5, 2013

### rqu1ntana

The problem is that its for a test and i just want to be sure what i did was right. This is what i did,

I used the formula Vf2=Vi2-2g(y-yi), where Vi2 is the initial velocity, g is gravity=9.8, y is 0, and yi is the height.

from all the data given this is what it looks like, Vf=(102-(2*9.8*(-15)))1/2

The result i get from this is 13.56m/sec, i this right?

4. Nov 5, 2013

### tiny-tim

hi rqu1ntana!
yes that looks fine … you've used conservation of energy (so the 25° doesn't matter)

except that you keyed in -110 instead of 100 !