The altitude of a kite is graphed here (the y-axis is in increments of 10 feet; the t-axis is in minutes). Over which intervals is the kite accelerating upward?

paste.pics/1a51dc876019fc4dd47240a035d8f5bf
Go to this website for the graph

3 answers

the acceleration is positive when the velocity y' is increasing. That is, where y" > 0. In other words, where y is concave up.
The correct answer was (3, 6.3) on Apex
In which intervals does the length of the kite string increase?