The car drove in a straight line all the time. For several hours he moved at a constant speed of 40 km / h

The car drove in a straight line all the time. For several hours he moved at a constant speed of 40 km / h, then stood in a traffic jam for 1 hour, after which he continued to move at a speed of 60 km / h for another 2 hours and arrived at his destination. Find the average speed for the entire journey.

V1 = 40 km / h.

t1 = 2 h.

t2 = 1 h.

V2 = 0 m / s.

t3 = 2 h.

V3 = 60 km / h.

Vav -?

To find the average vehicle speed Vav, it is necessary to divide the entire path S it has traveled by the time of its passage t: Vav = S / t.

The travel time of the entire travel path is expressed by the sum: t = t1 + t2 + t3, where t1 is the travel time on the first part of the route, t2 is the idle time in a traffic jam, t3 is the travel time on the second part of the route.

t = 2 h + 1 h + 2 h = 5 h.

The entire traversed path S will be the sum: S = S1 + S3.

With uniform rectilinear motion, the path is expressed by the formulas: S1 = V1 * t1 and S3 = V3 * t3.

S1 = 40 km / h * 2 h = 80 km.

S3 = 60 km / h * 2 h = 120 km.

S = 80 km + 120 km = 200 km.

Vav = 200 km / 5 h = 40 km / h.

Answer: the average speed of the vehicle during travel was Vav = 40 km / h.