2. How fast would the spaceship have to move in order for your [moving] mass to
ID: 1271509 • Letter: 2
Question
2. How fast would the spaceship have to move in order for your[moving] mass to be double your resting mass? What would you see if
you stepped on a scale while traveling in your spaceship at this
speed?
Identify the unifying physical principle that ties all three of these
investigations together and explain how they are connected.
Use the following equation for relativistic mass to solve this problem
and post your answer in the Dropbox. Make sure to show how you arrived
at your answers. If you need assistance or have any questions please
post in the Week 4 Assignment Discussion by following the link below.
Equation for relativistic mass
m = m' / ? (1 - v 2 /c 2 )
Where:
m = the relative mass of a moving object
m' = the mass of the object at rest
v = the velocity of the object
c = the speed of light 2. How fast would the spaceship have to move in order for your
[moving] mass to be double your resting mass? What would you see if
you stepped on a scale while traveling in your spaceship at this
speed?
Identify the unifying physical principle that ties all three of these
investigations together and explain how they are connected.
Use the following equation for relativistic mass to solve this problem
and post your answer in the Dropbox. Make sure to show how you arrived
at your answers. If you need assistance or have any questions please
post in the Week 4 Assignment Discussion by following the link below.
Equation for relativistic mass
m = m' / ? (1 - v 2 /c 2 )
Where:
m = the relative mass of a moving object
m' = the mass of the object at rest
v = the velocity of the object
c = the speed of light
Explanation / Answer
We are looking for a Lorentz factor of 2, so
1/sqrt(1-v^2)=2
sqrt(1-v^2)=1/2
1-v^2=1/4
v^2=3/4
v=sqrt(3/4)
.866c
Today, many physicists reserve the word "mass" exclusively for invariant mass. When considering a body in one motion, they use the expression for the momentum and energy. The relativistic mass is thus a redundant quantity as it is proportional to the total energy of the body. Nevertheless, many popular books and textbooks, and some other physicists, still teach the relativistic mass concept.
.........................
relativistic mass: m = m0 / sqrt(1 - (v/c)^2)
mass doubles, so m = 2 * m0, m0 kicks out. Follows:
2 = 1 / sqrt(1 - (v/c)^2)
==> 1 - (v/c)^2 = 1/4
==> v/c = sqrt(3/4)
==> v = sqrt(3/4) c = 0.866 c
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