One dimensional motion- object accelerating straight downwards

Click For Summary

Homework Help Overview

The problem involves a rocket accelerating downwards from a height, with its acceleration increasing over time according to a specific function. The original poster seeks to determine when the rocket will hit the ground and its velocity at that moment.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • The original poster attempts to apply a kinematic equation for constant acceleration, which raises questions about the validity of this approach given the non-constant nature of the acceleration.
  • Some participants question the appropriateness of using the constant acceleration formula and suggest revisiting the definition of acceleration.
  • Another participant mentions integrating to find the position function and subsequently solving for time and velocity.

Discussion Status

The discussion is active, with participants providing feedback and questioning the assumptions made by the original poster. There is an indication of productive exploration as different methods are considered, but no consensus has been reached on a specific approach.

Contextual Notes

The original poster expresses confusion regarding the application of kinematic equations, highlighting a potential misunderstanding of the problem's dynamics. The discussion reflects on the need to carefully interpret the problem before applying equations.

texan14
Messages
7
Reaction score
0
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



xf = xi + vi*t + (1/2)*a*t2

The Attempt at a Solution



xf = (0) + vi*t + (1/2)*β*t2

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


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
 


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
 


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

ehild
 

Similar threads

Are suvat equations valid in 2 dimensional motion for constant acceleration?
  • · Replies 5 ·
Replies
5
Views
2K
Determine when (m), and how long the rocket should fire.
  • · Replies 2 ·
Replies
2
Views
2K
Ball launched from a height of 5 meters --- Projectile motion
  • · Replies 12 ·
Replies
12
Views
1K
Finding proper value for centripetal acceleration in a plane rising up
  • · Replies 16 ·
Replies
16
Views
957
Kinematics: Motion in One Direction: Car Chase
  • · Replies 9 ·
Replies
9
Views
3K
Acceleration of system related to rolling motion and pulley
  • · Replies 35 ·
2
Replies
35
Views
5K
How Long Does a Sprinter Accelerate Before Reaching Top Speed?
  • · Replies 1 ·
Replies
1
Views
2K
Application of one dimensional force - Dynamics
  • · Replies 2 ·
Replies
2
Views
14K
1D Angular Motion with different velocity stages
  • · Replies 3 ·
Replies
3
Views
2K
Superposition of two one-dimensional harmonic waves
  • · Replies 10 ·
Replies
10
Views
2K