Velocity and Displacement?

Question

How is this solved? =/

A car travels along a straight stretch of road. It proceeds for 14.1 mi at 59 mi/h, then 29.3 mi at 49 mi/h, and finally 44.2 mi at 35.4 mi/h. What is the car's average velocity during the entire trip? Answer in units of mi/h.

Answer 1

let (t1, t2, t3) in hours be time taken is respective journey (s)

t1 = x1/v1, t2 = x2/v2, t3 = x3/v3

average velocity = displacement/total time

v(av) = [x1+x2+x3]/(t1+t2+t3)

remember> in rectilinear motion, displacement = total distance

v(av) = [14.1+29.3+44.2]/[14.1/59 + 29.3/49 + 44.2/35.4]

v(av) = [87.6]/[2.0855]

= 42 mi/h

Answer 2

To figure this answer out, we need to know how far the car traveled, and how long it took to get there.

Assuming the stretches were all in the same direction, the total distance traveled would be 14.1mi + 29.3mi + 44.2mi = 87.6 mi.

The 14.1mi segment was driven at 59mi/h, so to figure out how many hours it took, divide 14.1mi by 59 mi/hr = 14.1/59 hr.

So the total amount of time is 14.1/59 + 29.3/49 + 44.2/35.4 hr. = 2.0856hr

And the average speed would be 87.6mi/2.0856hr = 42.0023mi/hr