IB Physics HL A 5 7 Hl Relativistic Velocity Addition Topic Practice

An observer P sitting in a train moving at a speed v measures that his journey takes a time $\Delta t_{\mathrm{p}}$. An observer Q at rest with respect to the ground measures that the journey takes a time $\Delta t_{\mathrm{Q}}$.

A second train is moving at a velocity of -0.70 c with respect to the ground.

Calculate the speed of the second train relative to observer P .