another modelling question i cant get my head around Watch

13.oswin.tsang
Badges: 8
Rep:
?
#1
Report Thread starter 3 weeks ago
#1
i need help with q

10) a cyclist is travelling along a straight road.the distance in metres of the cyclist from a fixed point after t seconds is modelled by the function f(t), where f'(t)=5+2t and f(0)=0
a) find expression for f(t)
b) calculate the time taken for the cyclist to travel to 100m

ive done part a) which is 5t+t^2+c

on part b) i have only concluded that we are asked to find f(100) and i have found that C is 0, becuase
f(0)=5(0)+(0)^2+c = 0,
i think im doing this wrong. someone help
0
reply
Pangol
Badges: 12
Rep:
?
#2
Report 3 weeks ago
#2
(Original post by 13.oswin.tsang)
i need help with q

10) a cyclist is travelling along a straight road.the distance in metres of the cyclist from a fixed point after t seconds is modelled by the function f(t), where f'(t)=5+2t and f(0)=0
a) find expression for f(t)
b) calculate the time taken for the cyclist to travel to 100m

ive done part a) which is 5t+t^2+c

on part b) i have only concluded that we are asked to find f(100) and i have found that C is 0, becuase
f(0)=5(0)+(0)^2+c = 0,
i think im doing this wrong. someone help
You are right about c being 0, but not about f(100).

f is a function of time. Give it a time, and it tells you the distance from the starting point. You are told the distance from the starting point, and you need to find the time that goes with it. Does this help you to see what the equation you have to solve is?
0
reply
RDKGames
  • Community Assistant
Badges: 20
Rep:
?
#3
Report 3 weeks ago
#3
(Original post by 13.oswin.tsang)
i need help with q

10) a cyclist is travelling along a straight road.the distance in metres of the cyclist from a fixed point after t seconds is modelled by the function f(t), where f'(t)=5+2t and f(0)=0
a) find expression for f(t)
b) calculate the time taken for the cyclist to travel to 100m

ive done part a) which is 5t+t^2+c

on part b) i have only concluded that we are asked to find f(100) and i have found that C is 0, becuase
f(0)=5(0)+(0)^2+c = 0,
i think im doing this wrong. someone help
TBH, you haven't done part (A) completely. In this part of the question you need to determine the value of c by using the initial condition f(0) = 0.

You actually spilled this into part (B) where you are actually correct that c=0.

So f(t) = 5t + t^2.

So finish off the question. We seek t such that f(t) = 100.

Have a go at it first but if you can't see a way to proceed then here's a hint:
Spoiler:
Show

You want to solve the equation 5t + t^2 = 100 for a solution t=t^* > 0. Notice that it's a quadratic equation, so it should be no trouble!
Last edited by RDKGames; 3 weeks ago
0
reply
13.oswin.tsang
Badges: 8
Rep:
?
#4
Report Thread starter 3 weeks ago
#4
thank you.
0
reply
X

Quick Reply

Attached files
Write a reply...
Reply
new posts
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

University open days

  • University of Birmingham
    Postgraduate Open Day Postgraduate
    Wed, 20 Mar '19
  • King's College London
    Postgraduate Taught Courses - Arts & Sciences - Strand Campus Postgraduate
    Wed, 20 Mar '19
  • University of East Anglia
    All Departments Open 13:00-17:00. Find out more about our diverse range of subject areas and career progression in the Arts & Humanities, Social Sciences, Medicine & Health Sciences, and the Sciences. Postgraduate
    Wed, 20 Mar '19

Where do you need more help?

Which Uni should I go to? (35)
14.34%
How successful will I become if I take my planned subjects? (21)
8.61%
How happy will I be if I take this career? (50)
20.49%
How do I achieve my dream Uni placement? (35)
14.34%
What should I study to achieve my dream career? (30)
12.3%
How can I be the best version of myself? (73)
29.92%

Watched Threads

View All