Question

3. A man is riding his bicycle at 8.5 m/s. When a car cuts in
| front of him, he decelerates at a rate of -2.8 m/s2. How
long does it take him to stop? How far has he moved during
that time frame?​

Answer 1

Explanation:

We are given,

u = 8.5 m/s

a = -2.8 m/s²

v = 0

t = ?

s = ?

We know that,

v = u + at

Putting in the values we get,

0 = 8.5 + (-2.8)t

-8.5 = -2.8t

t = -8.5/-2.8

t = 3.03 s ~ 3 s

Now,

v² - u² = 2as

so, s = (v² - u²)/2a

s = (0² - (8.5)²)/2(-2.8)

s = -72.25/-5.6

s = 12.90 m ~ 13 m

Thus, it took him approximately 3 seconds to stop and covered a distance of approximately 13m

Hope it helped and you understood it........All the best