Hello everyone, I am new to this forum and very much interested in physics. As a student, I find motion is my weakness in this subject. Hopefully everyone can help me out :) 1. The problem statement, all variables and given/known data While driving North at a velocity of 28ms^-1 relative to the ground, a man notices a cyclist crossing the road ahead. The cyclist is travelling West at 7ms^-1 relative to the ground. 2. Relevant equations (a) What is the velocity of the cyclist relative to the driver? (b) What is the velocity of the driver relative to the cyclist? 3. The attempt at a solution For (a) I thought of subtracting the two values, however (b) has the values the other way around, therefore it doesn't make sense to me. Perhaps I could use the Pythrogem's theorem a^2 + b^2 = c^2 but would it be correct? I'm very unsure of quoting the directions in the answers. Thankyou.