Velocity Decay Curve for a Rocket

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Discussion Overview

The discussion revolves around calculating the initial velocity (A) of a rocket using a velocity decay curve represented by an exponential function. Participants are exploring how to adjust the initial velocity to achieve a specific distance traveled (15m) over a time interval of 0 to 4 seconds. The scope includes mathematical reasoning and problem-solving related to physics.

Discussion Character

  • Homework-related
  • Mathematical reasoning

Main Points Raised

  • One participant expresses confusion about how to start solving the problem of determining the initial velocity A, given the distance traveled and the decay curve equation.
  • Another participant suggests that the equation has three knowns (time, distance, and decay constant) and one unknown (A), implying that it can be solved for A.
  • A participant questions whether A should be set to 15, as the goal is to achieve a distance of 15m at t=4 seconds.
  • One participant proposes that replacing A with 10.22 in the formula yields a distance of approximately 15.0097, suggesting that A could be 10.22.
  • Another participant reiterates the approach of rearranging the equation to solve for A, confirming the known variables and the unknown.

Areas of Agreement / Disagreement

Participants generally agree that the problem involves three knowns and one unknown, but there is uncertainty about the correct value of A and how to calculate it. Multiple views on the value of A exist, with some proposing 15 and others suggesting 10.22.

Contextual Notes

There are limitations regarding the assumptions made about the decay constant and the specific conditions under which the calculations are performed. The discussion does not resolve how to definitively calculate A or the implications of the chosen values.

pete321
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Homework Statement
suggest a new initial velocity A of the rocket
Relevant Equations
$$\large \int_0^{t_L} A e^{\frac{-t}{\tau}} \text{d}t = A \tau \left( 1- e^{\frac{-t}{\tau}} \right)$$
I am trying to solve the problem below. I have previously calculated from 0 to 4 seconds how far the rocket will travel in each second. I am stuck now as to how to start this problem. I have searched but unable to find the answer. Do i need to rearrange this? A is currently 14 which does not get the rocket to travel 15m in 4 seconds. Once i know how to start this i want to solve on my own so i understand how to complete this.

The integral of the decay curve of the form:
$$Ae^{\frac{-t}{\tau}}$$ This can be expressed as follows:

$$\large \int_0^{t_L} A e^{\frac{-t}{\tau}} \text{d}t = A \tau \left( 1- e^{\frac{-t}{\tau}} \right)$$

$$a = 14$$

$$\tau = 1.6$$

$$ t = 4$$Given this information, suggest a new initial velocity A of the rocket, which will allow the rocket to travel 15m in the same time interval of 0 to t=4.
 
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Looks to me like you have an equation with 3 knowns (t, r, and distance) and 1 unknown (a). Can you solve for the 1 unknown?
 
Thank you for your reply. No this is where i am confused. Is A now 15. As when t is 4 seconds the distance will be 15 not 14? I just don't understand how to calculate this. I have been searching for hours with no luck
 
replacing 14 with 10.22 in the formula =15.0097. So would A be 10.22? If so just need to work out how to calculate it
 
pete321 said:
replacing 14 with 10.22 in the formula =15.0097. So would A be 10.22? If so just need to work out how to calculate it
Like I said, you have 3 knowns and 1 unknown.
D=Ar(1-e-t/r), and we know D, r, and t.
So you rearrange the equation to solve for A.
 
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