Question

a bicyclist is traveling at 5 m/s when he begins to brake at 4m/s^2. how fast is he traveling after 5 seconds?

Answer 1

Answer:

Zero (or -15 m/s if he reverses the direction)

Explanation:

The motion of the bicyclist is a uniform accelerated motion, so we can use the following suvat equation:

$v=u+at$

where:

u is the initial velocity

v is the final velocity

a is the acceleration

t is the time

For the cyclist in the problem, we have:

u = 5 m/s

$a=-4 m/s^2$ (negative because it is a deceleration)

If we substitute t = 5 s, we find the velocity of the bike after that time:

$v=5+(-4)(5)=-15 m/s$

Which means that the cyclist is travelling at 15 m/s in the opposite direction: however, normally when you apply brakes you just slow down until stop, and the direction does not reverse; this means that the byciclist after 5 seconds has came to a stop.