One dimensional motion- object accelerating straight downwards

[texan14]

One dimensional motion-- object accelerating straight downwards

Homework Statement

A rocket, initially at rest, is fired at "t = 0" vertically down from a building of height "H". The rocket's acceleration, including the effects of gravity, is downwards with increasing magnitude given by a(t) = βt, where "β" is a known constant. When does it hit the ground and how fast is it going when it hits?

Homework Equations

x_f = x_i + v_i*t + (1/2)*a*t²

The Attempt at a Solution

x_f = (0) + v_i*t + (1/2)*β*t²

I plugged everything into this equation, but it doesn't look right. I'm really confused. thanks in advance

 

[ehild]

Hi Texan14,

Is the acceleration constant? If not, why do you want to use the formula for constant acceleration?

Go back to the definition of acceleration.

ehild

 

[texan14]

I decided to integrate until I got the position function and solved for "t" and just plugged that into v(t). Thank you for your help, I don't know why I wanted to use that equation! haha

 

[ehild]

It does not hurt to read the the problem before plugging in everything to everywhere...

ehild