# Questions tagged [mass]

The property of an object that determines how much it responds to a force in Newtonian mechanics, and how much it interacts with gravity in the Newtonian framework. Mass also refers to the intrinsic energy of a particle in particle physics. This tag does also cover effective mass.

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### Problem with equation of thrust in a system of variable mass

The equation for force on a system of variable mass (e.g. a rocket thrust equation) is $$F=-u\frac{\mathrm{d}m}{\mathrm{d}t}$$ where $u$ is the velocity of the escaping gases with respect to the ...
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### ADM mass calculation for the BTZ black hole

Considering a non-rotating and non-charged 2+1 dimensional black hole, known as the BTZ black hole which obtained by adding a negative cosmological constant $\Lambda=-\frac{1}{l^2},l\ne0$ to the ...
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### Black hole production via light speed [duplicate]

As a test particle with rest mass approaches $c$ relativistic mass increases to infinity, does this mean that the energy required to continue the acceleration will create a black hole (as time also ...
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### Why do objects with greater length feel heavier - and how to calculate perceived weight?

Consider this situation: As part of some training, you are asked to pull an object that is 100 feet long, weighing approximately 218 pounds across a distance of 310 feet (fire hose across concrete if ...
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### How did Einstein figure out mass (and hence energy) bends spacetime?

I can understand that once I fix the velocity of light at $c$, there is a relative variation in space-time based on special relativity (inertial frame of reference). It's not clear to me how Einstein ...
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### Can two objects of different mass experience the same air resistance? [duplicate]

This question is assuming that the objects have the same shape and size, but different masses. I know that all objects have the same gravitational acceleration on earth, which is about 9.8 m/s^2. ...
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### Is it necessary for constant mass of system to use Newton's 2nd law? [duplicate]

Is it necessary for the mass of the system to be constant to use Newton's 2nd law (here the mass of the bodies in the system can change but the total mass of system can't)
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