I can't comprehend impulse = momentum

In summary, the conversation discusses a calculation involving the force, mass, and acceleration of a rocket, as well as the time it takes to travel a distance of 1000m. It is determined that the rocket must apply a thrust of 50N for 102.440s in order to reach the required speed. However, it is noted that there may be multiple solutions to this question and that the rocket may not be activated for the entire time it takes to travel 1000m.
  • #1
Pushies
3
0
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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  • #2
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.)
 
  • #3
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.)
 
  • #4
Sorry for the confusion guys. Iwas tired at the moment of writing, now i can solve it after some time of contemplating. Thanks
 

FAQ: I can't comprehend impulse = momentum

What is impulse and momentum?

Impulse and momentum are two related concepts in physics. Impulse is defined as the change in momentum of an object over a certain period of time. Momentum, on the other hand, is the product of an object's mass and velocity. In simpler terms, impulse is the force applied to an object over time, while momentum is the amount of motion an object has.

What is the relationship between impulse and momentum?

The relationship between impulse and momentum is described by Newton's second law of motion, which states that the force applied to an object is equal to the change in momentum over time. This means that the greater the impulse applied to an object, the greater its change in momentum will be.

Why is it difficult to comprehend the relationship between impulse and momentum?

The relationship between impulse and momentum can be difficult to comprehend because it involves understanding both force and motion. It also requires an understanding of calculus, as impulse and momentum are both defined as the integral of force and velocity, respectively, over time.

How are impulse and momentum used in real life?

Impulse and momentum are used in many real-life situations, such as in sports, car accidents, and rocket launches. In sports, athletes use the concept of impulse to increase their momentum and achieve greater speed or distance. In car accidents, the force of impact is directly related to the change in momentum, which is why it is important to wear seatbelts to decrease the impulse and reduce the force of impact. In rocket launches, a large amount of impulse is applied to the rocket to increase its momentum and propel it into space.

What are some common misconceptions about impulse and momentum?

One common misconception is that impulse and momentum are the same thing. While they are related, they are two distinct concepts. Another misconception is that only large forces can result in significant changes in momentum. In reality, even a small force applied over a long period of time can result in a large change in momentum. Lastly, some people may think that momentum can only be conserved in collisions, but it is actually conserved in all interactions, including explosions and rocket launches.

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