The length of a moving spaceship is 27.0 m according to an astronaut on the spaceship. If the spaceship is contracted by 14.5 cm according to an Earth observer, what is the speed of the spaceship?

I know L=27m
and delta L= 0.145
so our contracted length is 26.855

so what should I can I do from here to solve it?

To solve this problem, you can use the concept of length contraction in special relativity. The length contraction formula can be expressed as:

L' = L * sqrt(1 - (v^2 / c^2))

Where:
L' is the contracted length observed by the Earth observer,
L is the original length observed by the astronaut on the spaceship,
v is the velocity of the spaceship, and
c is the speed of light.

In this case, you know L = 27.0 m, and the contracted length L' = 26.855 m.

To find the speed of the spaceship (v), you need to rearrange the formula and solve for v:

v = c * sqrt(1 - (L'^2 / L^2))

Substituting the given values:

v = c * sqrt(1 - ((26.855^2) / (27^2)))

Now, you can calculate the speed of the spaceship by substituting the values into the equation and solving for v. The speed of light (c) is approximately 3.00 x 10^8 m/s.

Note: Make sure to convert all the measurements to SI units before performing the calculations.