Question

Car A and car B are travelling down a straight road.Car A is travelling at 15m/s and accelerating at 2m/s².Car B starts from speed 0 but accelerates at 4m/s².After how many seconds car A and B will be travelling at the same speed?

Answer 1

Let's write the velocities of cars A and B:

$$v_A=v_{0A}+a_{0A}t,$$ $$v_B=v_{0B}+a_{0B}t.$$

Cars A and B will be travelling at the same speed when $v_A=v_B$:

$$v_{0A}+a_{0A}t=v_{0B}+a_{0B}t,$$ $$15+2t=0+4t,$$ $$t=\dfrac{15\ \dfrac{m}{s}}{2\ \dfrac{m}{s^2}}=7.5\ s.$$