What Is the Final Speed of a Steel Ball Launched from a Platform?

[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?

 

[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)

 

[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 V_f²=V_i²-2g(y-y_i), where V_i² is the initial velocity, g is gravity=9.8, y is 0, and y_i is the height.

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

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

 

[tiny-tim]

hi rqu1ntana!

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

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

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 !