I'm not sure I understand what to do with what's given to me to solve this. I know it has to do with the relationship between velocity, acceleration and time.
At a distance of $45m$ from a traffic light, a car traveling $15 m/sec$ is brought to a stop at a constant deceleration.
a. What is the value of deceleration?
b. How far has the car moved when its speed has been reduced to $3m/sec$?
c. How many seconds would the car take to come to a full stop?
Can somebody give me some hints as to where I should start? All I know from reading this is that $v_0=15m$, and I have no idea what to do with the $45m$ distance. I can't tell if it starts to slow down when it gets to $45m$ from the light, or stops $45m$ from the light.
Edit:
I do know that since accelleration is the change in velocity over a change in time, $V(t)=\int a\ dt=at+C$, where $C=v_0$. Also, $S(t)=\int v_{0}+at\ dt=s_0+v_0t+\frac{1}{2}at^2$. But I don't see a time variable to plug in to get the answers I need… or am I missing something?
Best Answer
Hint: Constant acceleration means that the velocity $v(t)=v(0)+at$ where $a$ is the acceleration. The position is then $s(t)=s(0)+v(0)t+\frac 12 at^2$. You should be able to use these to answer the questions.