Rates of change (1 Viewer)

[Jago]

Quick question, when do i use f(x) and when do i use f'(x)?

 

[smallcattle]

can you give me an example?

 

[gordo]

f'(x) is the derrivative

for example, if u have they tell u the distance is given by f(x) = x^2 + 3x - 1
and say find the velocity, u will find f'(x)
i.e 2x + 3

 

[Jago]

(a) Sand is tipped from a truck onto a pile. The rate, R kg/s, at which the sand is
flowing is given by the expression R = 100t – t 3, for 0 =< t =< T, where t is
the time in seconds after the sand begins to flow.
(i) Find the rate of flow at time t = 8.
(ii) What is the largest value of T for which the expression for R is physically
reasonable?
(iii) Find the maximum rate of flow of sand.
(iv) When the sand starts to flow, the pile already contains 300 kg of sand.
Find an expression for the amount of sand in the pile at time t .
(v) Calculate the total weight of sand that was tipped from the truck in the
first 8 seconds.

 

[JayWalker]

(a) Sand is tipped from a truck onto a pile. The rate, R kg/s, at which the sand is
flowing is given by the expression R = 100t – t 3, for 0 =< t =< T, where t is
the time in seconds after the sand begins to flow.
(i) Find the rate of flow at time t = 8.
(ii) What is the largest value of T for which the expression for R is physically
reasonable?
(iii) Find the maximum rate of flow of sand.
(iv) When the sand starts to flow, the pile already contains 300 kg of sand.
Find an expression for the amount of sand in the pile at time t .
(v) Calculate the total weight of sand that was tipped from the truck in the
first 8 seconds.

(i) You would use f^'(x) for rate
(ii) Imagine that the expression R = 100t - t 3 or what ever it is as a curve, use f^'(x) let that = 0 find stat pts
(iii) use f^''(x) as this is rate of change of f^'(x)

Yeah understand?

 

[Jago]

alright, thanks.

Damn family vacation. Forgot EVERYTHING.

 

[Tommy_Lamp]

So if you have to find the rate of change/flow of something, its f'(x)
if you want the maximum/minimum rate of change/flow, its f"(x)
Ok I have a question, when doing the maximum rate, what numbers would we put in the formula? If it would help could someone maybe solve the above question

 

[Seraph]

?

R = 0

dr/dt with point < 0

?

i think...