Question

Two identical trains A and B move with equal speeds on parallel tracks along the equator. A moves from east to west and B, from west to east. Which train will exert greater force on the tracks?

• A. A
• B. B
• C. They will exert equal force.
• D. The mass and the speed of each train must be known to reach a conclusion.

Answer 1

Answer: (A)

A

Answer 2

Let v = speed of each train relative to the earth’s surface, v_E = speed of earth’s surface relative to the earth’s axis, v_A, v_B = speeds of A and B relative to the earth’s axis.

Then, v_A = v_E- v, v_B = v_B + v.

N_A = mg - m$\left( \frac{v_{A}^{2}}{R} \right)$, N_B = mg - m$\left( \frac{v_{B}^{2}}{R} \right)$.

⇒ N_A > N_B.