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http://prntscr.com/16ccxmz Please help. I do not know how to start off with this question
http://prntscr.com/16cd1n6 I need help with part B only for this question (My answer 270 seconds) Not sure if right.
Original post by helpplease346
http://prntscr.com/16ccxmz Please help. I do not know how to start off with this question
http://prntscr.com/16cd1n6 I need help with part B only for this question (My answer 270 seconds) Not sure if right.

help
Reply 2
Original post by helpplease346
http://prntscr.com/16ccxmz Please help. I do not know how to start off with this question
http://prntscr.com/16cd1n6 I need help with part B only for this question (My answer 270 seconds) Not sure if right.

The first question is just an exercise in maximization, which requires calculus. Have you covered differentiation yet?
Original post by davros
The first question is just an exercise in maximization, which requires calculus. Have you covered differentiation yet?

We have done differentiation in pure but not mechanics. (Edexcel)
Reply 4
Original post by helpplease346
We have done differentiation in pure but not mechanics. (Edexcel)

well it's the same principle - you can actually forget the "mechanics" here :smile: You have a function of t and you want to find its maximum value, so what do you do?
Original post by davros
well it's the same principle - you can actually forget the "mechanics" here :smile: You have a function of t and you want to find its maximum value, so what do you do?

Differentiation (1-t^2) which becomes -2t. After this idk what to do
Reply 6
Original post by helpplease346
Differentiation (1-t^2) which becomes -2t. After this idk what to do


That's not quite right is it? The function is t(1-t^2), not just 1-t^2 :smile:
Original post by davros
That's not quite right is it? The function is t(1-t^2), not just 1-t^2 :smile:

1-2t. After this what do you do ?
Reply 8
Original post by helpplease346
1-2t. After this what do you do ?

Where does the "-2t" come from? Your original function is t(1-t^2) = t - t^3, so what do you get when you differentiate?
Original post by davros
Where does the "-2t" come from? Your original function is t(1-t^2) = t - t^3, so what do you get when you differentiate?

Oh just realised i never times the t. differentiation = 1-3t^2. Then I guess you find the value of t which is sqrt 3/3. After this what do you do?
Reply 10
Original post by helpplease346
Oh just realised i never times the t. differentiation = 1-3t^2. Then I guess you find the value of t which is sqrt 3/3. After this what do you do?

Well technically you should check that your value is going to give a maximum, not a minimum - do you know what you have to do to check this?

Then the question wants the actual maximum value of the original function, so if you're happy you've got the correct value of t, just substitute this into the original function for the velocity and calculate the result - it's just manipulating some surds which should be straightforward :smile:
Original post by davros
Well technically you should check that your value is going to give a maximum, not a minimum - do you know what you have to do to check this?

Then the question wants the actual maximum value of the original function, so if you're happy you've got the correct value of t, just substitute this into the original function for the velocity and calculate the result - it's just manipulating some surds which should be straightforward :smile:

Thank you I got to the answer by putting the sqrt 3/3 into the original question

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