Hey, can someone explain this velocity question to me? The answer is E, but I don't know why.

Question

anonymous · Answer

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johnweldon1993 · Answer

Well we can see when a function is increasing...by taking the derivative of the function...

If s'(t) > 0   we would have a function that is increasing on that interval

anonymous · Answer

Okay, I think I got confused on what the question was asking. When it said "the speed of the particle increasing" I thought that I would need to know when the velocity was increasing, so I found the acceleration vector. Could you explain why you must only find when the velocity is positive?

agent0smith · Answer

I think john misread it the same way i did. You want where:

acceleration is negative AND velocity is negative 

acceleration is positive AND velocity is positive

Those are where speed is increasing.

anonymous · Answer

OH. See, I just tried to find where acceleration was positive. I completely forgot the rules for speeding up and slowing down. Thanks!

agent0smith · Answer

No prob.