You are riding your bicycle at a speed of 12 ft/2.
Four seconds later, you come to a complete stop. Find the acceleration of your bicycle.
Help! and explain it too please?

Question

You are riding your bicycle at a speed of 12 ft/2.
Four seconds later, you come to a complete stop. Find the acceleration of your bicycle. 
Help! and explain it too please?

anonymous · Answer

$$v _{f}=v _{i}+at$$
0=12+a(4)
-3ft/s=a

valpey · Answer

Acceleration is the change in speed (or velocity) over time. In this case you decelerated from 12 feet per second to zero feet per second across a period of four seconds. On average over those four seconds your speed went down by 3 feet per second for each of those seconds. Hence your acceleration was negative three feet per second per second or:
$$-3ft/s^{2}$$

anonymous · Answer

yes; ft/s^2!

valpey · Answer

If your acceleration was perfectly constant over those four seconds, your speed at time 0 was 12ft/s; at time 1 was 9ft/s; at time 2 was 6ft/s; at time 3 was 3ft/s; and at time 4 was 0ft/s.