Moving along the highway, the cyclist drove 900 m at a speed of 15 m per

Moving along the highway, the cyclist drove 900 m at a speed of 15 m per s, and then on a bad road traveled 400 m at a speed of 10 m per s. Determine the average speed of the cyclist along the entire path.

S1 = 900 m.

V1 = 15 m / s.

S2 = 400 m.

V2 = 10 m / s.

Vav -?

Vav = S / t.

The entire distance traveled by the cyclist S will be the sum: S = S1 + S2.

S = 900 m + 400 m = 1300 m.

The time of the entire movement of the cyclist t will be the sum: t = t1 + t2.

The travel time on the first and second parts of the path is found by the formulas: t1 = S1 / V1 and t2 = S2 / V2.

t1 = 900 m / 15 m / s = 60 s.

t2 = 400 m / 10 m / s = 40 s.

Let’s find the time of the entire movement: t = 60 s + 40 s = 100 s.

Vav = 1300 m / 100 s = 13 m / s.

Answer: the average speed of a cyclist on the entire section of the highway was Vav = 13 m / s.