Rate of Change Question I have this equation for a rate of change problem below s=t^4−4t^3−20t^2+20t,t>=0 The question asks me At what time does the particle have a velocity of 20 m/s? How do i solve this? Basically what steps do I take to find at what time the particle has that velocity?

Jase Rocha

Jase Rocha

Answered question

2022-09-24

Rate of Change Questions?
I have this equation for a rate of change problem below
s = t 4 4 t 3 20 t 2 + 20 t , t 0
The question asks me
At what time does the particle have a velocity of 20 m/s?
How do i solve this? Basically what steps do I take to find at what time the particle has that velocity?

Answer & Explanation

seguidora1e

seguidora1e

Beginner2022-09-25Added 8 answers

If s is the distance as a function of time t, then the velocity is given by v = d s d t
Set this derivative d s d t to 20 and solve the cubic, with the constraint t>0, to get the value of t.
Note that the cubic you obtain can be factored easily.
Move your cursor over the gray area for the complete answer.
d s d t = 4 t 3 12 t 2 40 t + 20
Setting this to 20 gives us,
4 t 3 12 t 2 40 t + 20 = 20 4 t 3 12 t 2 40 t = 0 4 t ( t 2 3 t 10 ) = 0
This gives us
t ( t 5 ) ( t + 2 ) = 0
Since t>0, we get that t=5.

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