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Alevelhelp.1

How do I know that time is 3 at the maximum velocity?for part 15 b ?

(edited 11 months ago)

Reply 1

MindMax2000

Universities Forum Helper

Original post by Alevelhelp.1

How do I know that time is 3 at the maximum velocity?for part 15 b ?

It's a little difficult to read pages when they're flip on their side.

The max value of v is 4 from the equation: v = 4 - (2t/3 - 2)^2
From inspection, v = 4 when (2t/3 - 2)^2 = 0
Isolate t in (2t/3 - 2)^2 = 0

if you want to do things the long winded way (unnecessary), you will likely use the chain rule to keep things simple:
max v @ dv/dt = 0
let u = 2t/3 - 2
dv/dt = dv/du*du/dt
you will find that this is when t = 3

(edited 11 months ago)

Reply 2

davros

Original post by Alevelhelp.1

How do I know that time is 3 at the maximum velocity?for part 15 b ?

They've told you what v is - it's just 4 - A^2 where A is some expression involving t. This is just a quadratic with a max when A = 0, so you know what t has to be :smile: