Question

How fast will a 4 meter long car need to go in order to fit inside of a 3 meter long garage? (Give your answers in terms of c, the speed of light)

Answer 1

Apply the equation for length contraction:

$$L=L_0\sqrt{1-(v^2/c^2)}→v=c\dfrac{L}{L_0},\\\space\\ v_c=3/4=0.75c.$$