Question

Two (2) monster trucks are on a collision course in a monster truck event. Truck A is moving 15 m/s E with respect to the ground, while Truck B is moving 18 m/s W relative to the ground. What is the velocity of Truck B relative to Truck A?

Answer 1

Let $v_A = 15 m/s$ be the velocity of truck A, and $v_B = 18 m/s$ be the velocity of truck B with respect to ground. According to the velocity-addition formula, their relative velocity is:

$$u_A = v_A + v_B = 33m/s$$

in W direction. See more here (https://en.wikipedia.org/wiki/Velocity-addition_formula#Galilean_relativity)

Answer. 33 m/s.