Question

I am stuck on both of these questions. Would you please tell me if my reasoning is correct?

1. An object is dropped off a building. When comparing the average velocity of the object over equal time intervals, explain the difference between early time intervals and later time intervals

Would this be because the object would gain more speed as it gets closer to the ground?

2. the velocity of an object is given by the function v(t)=2t^3-t^2-15t. At which of the following times t is the object at rest?
a) 1
b)-2.5
c)3
d)5

I tried to solve this question by substituting each option into the equation to see which number would make v(t) equal zero. This did not work for me since b and c both made the equation equal zero.

Answer 1

#1 yes. the speed has a constant rate of increase

#2
v(t) = t(2t^2-t-15) = t(2t+5)(t-3)
You are correct, that b and c are both solutions. But doesn't negative time present a problem? I think that in the real world I'd have to go with just (c).