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A cube has a density of 2000kg/m3while at rest in the laboratory. What is the cube’s density as measured by an experimenter in the laboratory as the cube moves through the laboratory at 90%of the speed of light in a direction perpendicular to one of its faces?

Short Answer

Expert verified

ÒÏ=4600kg/m3.

Step by step solution

01

Given Information

We have given that, a cube has a density of 2000kg/m3.

The cube moves through the laboratory at 90%of the speed of light in a direction perpendicular to one of its faces.

02

Simplify

At rest, the cube has a density of 2000kg/m3. That is, a cube with dimensions of lm×lm×lmhas a mass of 2000kg. The cube's dimension in the direction of motion is contracted as the cube moves at a speed of 0.9c:

localid="1650133944245" L'=1-vc21L'=1-(0.9·c)2c21L'=1-0.81·(1m)L'=0.436m

Because the other dimensions are unaffected, the new density is:

localid="1650133299285" ÒÏ=2000kg1m×1m×0.436mÒÏ=4600kg/m3

Therefore, Cubes density isÒÏ=4600kg/m3.

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