What is the average speed of an object that is not moving at t=0t=0 and accelerates at a rate of a(t) =5-t^2/4a(t)=5t24 on t in [2,4]t[2,4]?

1 Answer
Aug 18, 2017

"average speed" = 12.5average speed=12.5 "m/s"m/s

Explanation:

We're asked to find the average speed of a particle over a time interval, given its acceleration as a function of time.

The equation for average speed is

"average speed" = "distance traveled"/"time interval"average speed=distance traveledtime interval

Position is the second integral of acceleration. The total distance traveled is different from the displacement because it is strictly positive. Therefore, to find the distance traveled from t in [2color(white)(l)"s", 4color(white)(l)"s"]t[2ls,4ls], we take the absolute value (so that it is positive) of the definite integral from 22 to 44:

"distance traveled" = int_2^4intcolor(white)(l)|5-(t^2)/4|color(white)(l)dtcolor(white)(l)dt = color(red)(ul(25color(white)(l)"m"

The time interval is 2 "s", so we have

color(blue)("average speed") = (color(red)(25color(white)(l)"m"))/(2color(white)(l)"s") = color(blue)(ulbar(|stackrel(" ")(" "12.5color(white)(l)"m/s"" ")|)