helpplease346
Badges: 9
Rep:
?
#1
Report Thread starter 1 month ago
#1
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.
0
reply
helpplease346
Badges: 9
Rep:
?
#2
Report Thread starter 1 month ago
#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.
help
0
reply
davros
  • Study Helper
Badges: 16
Rep:
?
#3
Report 1 month ago
#3
(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?
0
reply
helpplease346
Badges: 9
Rep:
?
#4
Report Thread starter 1 month ago
#4
(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)
0
reply
davros
  • Study Helper
Badges: 16
Rep:
?
#5
Report 1 month ago
#5
(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 You have a function of t and you want to find its maximum value, so what do you do?
0
reply
helpplease346
Badges: 9
Rep:
?
#6
Report Thread starter 1 month ago
#6
(Original post by davros)
well it's the same principle - you can actually forget the "mechanics" here 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
0
reply
davros
  • Study Helper
Badges: 16
Rep:
?
#7
Report 1 month ago
#7
(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
0
reply
helpplease346
Badges: 9
Rep:
?
#8
Report Thread starter 1 month ago
#8
(Original post by davros)
That's not quite right is it? The function is t(1-t^2), not just 1-t^2
1-2t. After this what do you do ?
0
reply
davros
  • Study Helper
Badges: 16
Rep:
?
#9
Report 1 month ago
#9
(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?
0
reply
helpplease346
Badges: 9
Rep:
?
#10
Report Thread starter 1 month ago
#10
(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?
0
reply
davros
  • Study Helper
Badges: 16
Rep:
?
#11
Report 1 month ago
#11
(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
0
reply
helpplease346
Badges: 9
Rep:
?
#12
Report Thread starter 1 month ago
#12
(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
Thank you I got to the answer by putting the sqrt 3/3 into the original question
0
reply
X

Quick Reply

Attached files
Write a reply...
Reply
new posts
Back
to top
Latest
My Feed

See more of what you like on
The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

Personalise

Are you tempted to change your firm university choice on A-level results day?

Yes, I'll try and go to a uni higher up the league tables (38)
28.57%
Yes, there is a uni that I prefer and I'll fit in better (12)
9.02%
No I am happy with my choice (74)
55.64%
I'm using Clearing when I have my exam results (9)
6.77%

Watched Threads

View All