- #1

Gadget

- 5

- 0

Car A leaves a city and travels along a straight road for 1.5 min at 60km/h. It then accelerates uniformly for 0.25 min until it reaches a speed of 80 km/h. It proceedes at that speed for 2.0 min, then decelerates uniformly for 0.50min until it comes to rest. Car B leaves the same city along the same road and accelerates uniformly for 1.6 min until it reaches a speed of 160km/h. It then decelerates uniformly until it comes to rest again after 1.6 min. How far will the two cars have traveled during the different stages?

This is as far as I completely understand it:

Car A:

1 step: conversion 60km/h = 1 km/min

therefore = 1.5 km

2 step: conversion 80km/h = 1.33 km/min

therefore v = vo + at

1.33 - 1 = a = 1.32km/min

--------

.25

here is confusion:

x = x0 + v0t + 1/2at^2

x = 1.5 + 1.33(.25 min) + (1/2)(1.32)(.25)^2

or

x = (1/2)(1.32)(.25)^2

?