# Instantaneous Velocity Car Problem

A car is stopped at a traffic light. It then travels along a straight road so that its distance from the light is given by x(t)= bt^2 -ct^3, where b = 2.40m/s^2 and c = 0.120 m/s^3. How do you calculate the average velocity of the car for the time interval t=0 to t=10.

I think that maybe I need to take the derivative of the equation but then what please help!

Related Introductory Physics Homework Help News on Phys.org
collinsmark
Homework Helper
Gold Member
Hello mopar969,
How do you calculate the average velocity of the car for the time interval t=0 to t=10.
If you only need to find the average velocity, simply calculate the total distance traveled, divided by the time it takes to get there.

Thank you. I cant believe that it was that simple. I was thinking instantaneous velocity that is why I was thinking about taking its derivative.
However, the question has another part to it that I am stuck on it says:

You're searching the time t when the velocity is 0.

x(t)= bt^2 -ct^3, this finds the displacement as a function of time. You'll need another equation (related to this one) to find the velocity as a function of time.

Would I need the derivative of the displacement function?

Yes that would give you the velocity.

My next problem is how do I get t by itself?

Never mind I realized that I could use the quadratic formula.