Question

A cube has a density of 1800 kg/m3 while 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 91.0 % of the speed of light in a direction perpendicular to one of its faces? You may want to review (Pages 1040 - 1043) .

Answer 1

Answer:

4341.44763 kg/m³

Explanation:

$\rho'$ = Actual density of cube = 1800 kg/m³

$\rho$ = Density change due to motion

v = Velocity of cube = 0.91c

c = Speed of light = $3\times 10^8\ m/s$

Relativistic density is given by

$\rho=\frac{\rho'}{\sqrt{1-\frac{v^2}{c^2}}}\\\Rightarrow \rho=\frac{1800}{\sqrt{1-\frac{0.91^2c^2}{c^2}}}\\\Rightarrow \rho=\frac{1800}{\sqrt{1-0.91^2}}\\\Rightarrow \rho=4341.44763\ kg/m^3$

The cube's density as measured by an experimenter in the laboratory is 4341.44763 kg/m³