Solving the Spaceship Problem: Comparing Forces

  • Thread starter Thread starter mrhoneycinnamo
  • Start date Start date
  • Tags Tags
    Spaceship
Click For Summary
SUMMARY

The discussion centers on the physics of two identical spaceships, A and B, where A is stationary and B is traveling at a constant speed. When both engines are activated simultaneously, participants debate whether the spaceship with the higher initial speed (B) experiences a different force due to its velocity. The consensus is that both spaceships feel the same force because force is determined by mass and acceleration, not initial speed, aligning with the principles of Galilean relativity.

PREREQUISITES
  • Understanding of Newton's laws of motion, particularly F=ma.
  • Familiarity with the concept of Galilean relativity.
  • Basic knowledge of propulsion mechanics and reaction forces.
  • Comprehension of the relationship between force, mass, and acceleration.
NEXT STEPS
  • Study the principles of Galilean relativity in more depth.
  • Explore Newton's laws of motion, focusing on force and acceleration.
  • Investigate propulsion mechanics, particularly in the context of space travel.
  • Examine the implications of initial velocity on force perception in different inertial frames.
USEFUL FOR

Physics students, aerospace engineers, and anyone interested in the dynamics of motion and force in space travel.

mrhoneycinnamo
Messages
8
Reaction score
0
dear friends, days ago on a physics forum I saw this interesting question regarding fixed power and speed of a spaceship. After thinking for a while I came up with my answer but I am not really sure its correct.So please tell me what you think the answer is.

The question is: imagine there are 2 identical spaceship(with 2 identical engines),1 in stationary state,other travels at constant speed in a straight direction.Now 2 engines starts, how do people in different spaceship feel about the force(or the acceleration)?

some people believe that the one with higher initial speed(lets call it spaceship B) "feels" more force acting on it, becoz of the formula p=fv(since p is fixed, f decreases while v increases).

Somehow I disagree with it.(tell me if i am wrong:))
here is my reasoning:
since the way spaceship's engine works is to utilise the reaction force of its emitted gas(i don't know how to describe it but i assume you understand:)), so the velocity in the formula has something to do with the gas.Since both spaceships A and B was in balanced state, after the engines starts(assuming they start at the same time), A and B would travel at the same accelerating speed at any given time(take their emitted gas as reference frame).since p=fv, f is the same.
so my conclusion is people in both spaceship would feel the same force when the engines start at the same time. If i am wrong about this, please tell me why.
 
Physics news on Phys.org
The "one with the higher initial speed" thinks that the other one is the one with the initial speed. Each spaceship thinks that they are the one that is stationary. And so each spaceship uses "v=0" in their own equation.

mrhoneycinnamo said:
so my conclusion is people in both spaceship would feel the same force when the engines start at the same time. If i am wrong about this, please tell me why.

Yes, I believe this conclusion is correct. (I didn't completely follow your reasoning, though.)
 
  • Like
Likes   Reactions: 1 person
"Force equals mass times acceleration". With the same acceleration, the same force will be felt. Initial speed is irrelevant. That goes back to "Gallilean relativity".
 
  • Like
Likes   Reactions: 1 person

Similar threads

Replies
6
Views
2K
Replies
8
Views
3K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 14 ·
Replies
14
Views
2K
  • · Replies 9 ·
Replies
9
Views
4K
  • · Replies 20 ·
Replies
20
Views
2K
  • · Replies 1 ·
Replies
1
Views
1K
  • · Replies 18 ·
Replies
18
Views
2K
Replies
1
Views
2K
  • · Replies 21 ·
Replies
21
Views
4K