At 2pm the coastguard spots a rowing dinghy 500m due South of his observation point. The dinghy has constant velocity(2+3
a)Find in terms of t, the position vector of the dinghy t seconds after 2pm
I got 2t+(-500+3t)
b)Find the distance of the dinghy from the observation point at 2:05pm
Help pls on part b no idea what to do talk me through what to do.
-
thefatone
- Follow
- 57 followers
- 3 badges
- Send a private message to thefatone
- Thread Starter
Offline3ReputationRep:- Follow
- 1
- 24-04-2016 13:10
-
Kevin De Bruyne
- Follow
- 609 followers
- 21 badges
- Send a private message to Kevin De Bruyne
- Very Important Poster
Offline21ReputationRep:Very Important Poster- Follow
- 2
- 24-04-2016 13:13
(Original post by thefatone)
At 2pm the coastguard spots a rowing dinghy 500m due South of his observation point. The dinghy has constant velocity(2+3
a)Find in terms of t, the position vector of the dinghy t seconds after 2pm
I got 2t+(-500+3t)
b)Find the distance of the dinghy from the observation point at 2:05pm
Help pls on part b no idea what to do talk me through what to do. -
thefatone
- Follow
- 57 followers
- 3 badges
- Send a private message to thefatone
- Thread Starter
Offline3ReputationRep:- Follow
- 3
- 24-04-2016 13:19
absolutely nothing for me i'm not seeing anything -
Kevin De Bruyne
- Follow
- 609 followers
- 21 badges
- Send a private message to Kevin De Bruyne
- Very Important Poster
Offline21ReputationRep:Very Important Poster- Follow
- 4
- 24-04-2016 13:21
Can you see any way of finding the distance between where the dinghy isand the observation point? -
thefatone
- Follow
- 57 followers
- 3 badges
- Send a private message to thefatone
- Thread Starter
Offline3ReputationRep:- Follow
- 5
- 24-04-2016 13:27
(Original post by SeanFM)
What does your diagram look like?
Can you see any way of finding the distance between where the dinghy isand the observation point? -
Kevin De Bruyne
- Follow
- 609 followers
- 21 badges
- Send a private message to Kevin De Bruyne
- Very Important Poster
Offline21ReputationRep:Very Important Poster- Follow
- 6
- 24-04-2016 13:30
You have fallen into a trap - look carefully at the units in the question and then the time it asks you where the dingy is in the question.
But with that diagram you can still work out the method of finding the distance between the position and the origin.
How do you find the distance between the origin and the position? (You can think of them as x and y co-ordinates if you like).
Hint:
Spoiler:ShowThe distance is represented by a line that you already have on your diagram. -
thefatone
- Follow
- 57 followers
- 3 badges
- Send a private message to thefatone
- Thread Starter
Offline3ReputationRep:- Follow
- 7
- 24-04-2016 13:35
(Original post by SeanFM)
What lovely paper
You have fallen into a trap - look carefully at the units in the question and then the time it asks you where the dingy is in the question.
But with that diagram you can still work out the method of finding the distance between the position and the origin.
How do you find the distance between the origin and the position? (You can think of them as x and y co-ordinates if you like).
Hint:Spoiler:ShowThe distance is represented by a line that you already have on your diagram. -
Kevin De Bruyne
- Follow
- 609 followers
- 21 badges
- Send a private message to Kevin De Bruyne
- Very Important Poster
Offline21ReputationRep:Very Important Poster- Follow
- 8
- 24-04-2016 13:38
(Original post by thefatone)
no idea, 100% clueless
Hint:
Spoiler:ShowYou can say that the origin has co-ordinates (0,0) if that helps. -
thefatone
- Follow
- 57 followers
- 3 badges
- Send a private message to thefatone
- Thread Starter
Offline3ReputationRep:- Follow
- 9
- 24-04-2016 13:42
(Original post by SeanFM)
Okay, let's look at an example. If you had the point (3,4) on a graph and I asked you to find the distance between that and the origin, how would you do it?
Hint:Spoiler:ShowYou can say that the origin has co-ordinates (0,0) if that helps. -
Kevin De Bruyne
- Follow
- 609 followers
- 21 badges
- Send a private message to Kevin De Bruyne
- Very Important Poster
Offline21ReputationRep:Very Important Poster- Follow
- 10
- 24-04-2016 13:43
(Original post by thefatone)
pythagorasso, how does that help with anything?
-
thefatone
- Follow
- 57 followers
- 3 badges
- Send a private message to thefatone
- Thread Starter
Offline3ReputationRep:- Follow
- 11
- 24-04-2016 13:44
-
Kevin De Bruyne
- Follow
- 609 followers
- 21 badges
- Send a private message to Kevin De Bruyne
- Very Important Poster
Offline21ReputationRep:Very Important Poster- Follow
- 12
- 24-04-2016 13:47
(Original post by thefatone)
it doesn'tso I'll go over what I've said before:
1. Remember to look at the units in the question and correct your position vector at 2:05.
2. Try and find the distance between the position vector and the origin using ... -
thefatone
- Follow
- 57 followers
- 3 badges
- Send a private message to thefatone
- Thread Starter
Offline3ReputationRep:- Follow
- 13
- 24-04-2016 13:49
(Original post by SeanFM)
There is not much more I can say without giving away the answerso I'll go over what I've said before:
1. Remember to look at the units in the question and correct your position vector at 2:05.
2. Try and find the distance between the position vector and the origin using ... -
thefatone
- Follow
- 57 followers
- 3 badges
- Send a private message to thefatone
- Thread Starter
Offline3ReputationRep:- Follow
- 14
- 24-04-2016 13:54
(Original post by SeanFM)
There is not much more I can say without giving away the answerso I'll go over what I've said before:
1. Remember to look at the units in the question and correct your position vector at 2:05.
2. Try and find the distance between the position vector and the origin using ... -
Kevin De Bruyne
- Follow
- 609 followers
- 21 badges
- Send a private message to Kevin De Bruyne
- Very Important Poster
Offline21ReputationRep:Very Important Poster- Follow
- 15
- 24-04-2016 14:24
(Original post by thefatone)
where's the 90° angle?
For your time question, look at the question and see if you can work it out.
(I am deliberately giving you as little as possible so you can work it out for yourself)
-
thefatone
- Follow
- 57 followers
- 3 badges
- Send a private message to thefatone
- Thread Starter
Offline3ReputationRep:- Follow
- 16
- 24-04-2016 16:20
(Original post by SeanFM)
Well, where is the 90 degree angle between (0,0) and (3,4)?
For your time question, look at the question and see if you can work it out.
(I am deliberately giving you as little as possible so you can work it out for yourself)
no idea, it's literally a guess i have no idea what i count time as maybe 5? 0.5? 0.005? i really don't know -
Kevin De Bruyne
- Follow
- 609 followers
- 21 badges
- Send a private message to Kevin De Bruyne
- Very Important Poster
Offline21ReputationRep:Very Important Poster- Follow
- 17
- 24-04-2016 16:29
(Original post by thefatone)
between the x-axis and line parallel to the y-axis but i'm not seeing how this helps me do this question :/ i don't know if it's a right angled triangle.
no idea, it's literally a guess i have no idea what i count time as maybe 5? 0.5? 0.005? i really don't know
I'll give you another hint for the time - 2:05 is 5 minutes after 2 o'clock, and your velocity vector is measured in metres per second. -
thefatone
- Follow
- 57 followers
- 3 badges
- Send a private message to thefatone
- Thread Starter
Offline3ReputationRep:- Follow
- 18
- 24-04-2016 16:37
(Original post by SeanFM)
(3,4) means that from (0,0) you go 3 to the right and 4 up. So you can draw a line 3 units to the right then 4 units up from that point, and then a straight line from (0,0) to (3,4) and there is your right angled triangle. The straight line represents the distance between the two points.
I'll give you another hint for the time - 2:05 is 5 minutes after 2 o'clock, and your velocity vector is measured in metres per second.
sooooo
i get
600+400
?
Last edited by thefatone; 24-04-2016 at 16:59. -
Kevin De Bruyne
- Follow
- 609 followers
- 21 badges
- Send a private message to Kevin De Bruyne
- Very Important Poster
Offline21ReputationRep:Very Important Poster- Follow
- 19
- 24-04-2016 16:41
(Original post by thefatone)
i see so the time t is 300 then? so i sub in 300 as t? .-.
sooooo
i get
600+400
?
(as long you understand why, if you don't just say
)
Okay, you're almost there. What next? -
thefatone
- Follow
- 57 followers
- 3 badges
- Send a private message to thefatone
- Thread Starter
Offline3ReputationRep:- Follow
- 20
- 24-04-2016 17:01
(Original post by SeanFM)
Correct.(as long you understand why, if you don't just say
)
Okay, you're almost there. What next?
soooo i'm done? 600+400
is my final answer? no... pythagoras
sothanks a ton
- 1
- 2
-
University of Sussex
-
University of Southampton
-
London Metropolitan University
-
University of Derby
-
Computer Science and Mathematics
Keele University
-
University of St Andrews
-
Initial Year for Extended Degree in Science - Mathematics
University of Hertfordshire
-
Computer Science and Mathematics with Industrial Experience (4 years)
University of Manchester
-
Mathematics and Music with a Year Abroad
Cardiff University
-
University of Stirling
We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.
- SherlockHolmes
- Notnek
- charco
- Mr M
- Changing Skies
- F1's Finest
- rayquaza17
- RDKGames
- davros
- Gingerbread101
- Kvothe the Arcane
- TeeEff
- The Empire Odyssey
- Protostar
- TheConfusedMedic
- nisha.sri
- claireestelle
- Doonesbury
- furryface12
- Amefish
- harryleavey
- Lemur14
- brainzistheword
- Rexar
- Sonechka
- TheAnxiousSloth
- EstelOfTheEyrie
- CoffeeAndPolitics
- an_atheist
- Labrador99
- EmilySarah00