Blue car traveling

Question

A driver in a blue car traveling at 50 km h^-1 sees a red car approaching in his rear view mirror. The red car is traveling at 60 km h^-1 and is 30m behind the blue car when first spotted.

A) how many seconds from the time driver of the blue car first noticed it until the red car passes the blue car?

B) how much farther down the road will the blue car travel in this time?

Answer 1

Change the velocities to m/s so v_b = 13.89 m/s and v_r = 16.67 m/s so now 30 + v_bt = v_rt so t(v_r -v_b) = 30m and t= 30/2.78 = 10.8 s when red car passes the blue car. Blue car travels 149.89 m in this time.