I can't comprehend impulse = momentum

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    Impulse Momentum
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Homework Help Overview

The discussion revolves around the relationship between impulse and momentum in the context of a rocket's thrust and its motion over a specified distance. Participants are examining calculations related to force, acceleration, and the time required for the rocket to travel 1000 meters.

Discussion Character

  • Exploratory, Assumption checking, Conceptual clarification

Approaches and Questions Raised

  • Participants are calculating acceleration and time based on force and mass, while questioning the assumptions about the thrust duration and the timing of the rocket's burn. Some are exploring the implications of impulse equating to momentum and discussing the conditions under which these calculations hold true.

Discussion Status

The discussion is active, with participants providing calculations and raising questions about the assumptions made in the problem. There is acknowledgment of potential confusion regarding the timing of the thrust application and the implications of the calculations presented. One participant has indicated a resolution to their confusion after further contemplation.

Contextual Notes

There are uncertainties regarding the timing of the thrust application and the interpretation of the problem statement, which may lead to multiple interpretations of the solution. Participants are also noting the importance of initial conditions in the context of impulse and momentum.

Pushies
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Homework Statement
A satellite with a mass of 1050kg without any momentum or influence of force is floating freely in space. Later, its rocket was activated, applying force of 50N for x seconds. The satellite travelled 1000m in y seconds. Find the time needed, x, to apply 50N.

So i used the equation f = ma to find a so that i can plug it in the equation s = ut + ½at ²
Relevant Equations
F = ma
S = ut + ½at ²
Here is my calculation:

F = ma
50N = 1050kg * a
a = 0.0476m/s²

S = ut + ½at ²
1000m = 0t + ½(0.0476)t²
t = 204.980s
y = 204.980s (time to travel 1000m)

since impulse = momentum,

F * t = mv
F * x = m * distance covered/y
50N * x = 1050kg * 1000m/204.980s
50N * x = 5122.450N⋅s
x = 102.440s

50N * 102.440s ≈ 1050kg * 4.88m/s

Does this mean that the rocket has to apply thrust of 50N for 102.440s to supply the speed needed to cover 1000m in 204.98s ?
 
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The wording is slightly confusing to me. Is the time interval ##y## measured after the burn has completed? Otherwise it seems to me that there are infinitely many solutions to this question.

(N.B. Also a tiny quibble from me, the impulse ##I## equals the change in momentum ##\Delta P##. But in your case, if the initial momentum is 0, the impulse is the final momentum.)
 
Pushies said:
Here is my calculation:

F = ma
50N = 1050kg * a
a = 0.0476m/s²

S = ut + ½at ²
1000m = 0t + ½(0.0476)t²
t = 204.980s
y = 204.980s (time to travel 1000m)
You are making the assumption that the rocket is activated for all the time it takes to reach 1000 m, which I think is incorrect.

The way I read the problem, you have two unknowns, x and y. What you will then get is x as a function of y. (Even if the rocket is activated for 1 s, it will eventually travel a distance of 1000 m, taking longer than of the rocket is activated for a longer time.)
 
Sorry for the confusion guys. Iwas tired at the moment of writing, now i can solve it after some time of contemplating. Thanks
 

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