Mechanics Watch

Al4stair
Badges: 11
Rep:
?
#1
Report Thread starter 7 months ago
#1
Hi, please can i have some help with this question:*https://scontent.fbhx2-1.fna.fbcdn.n...58&oe=5CAA49F6



I get this answer (4m):*https://cdn.discordapp.com/attachmen...24/unknown.png



The answer given in the video was just 2m. Am i wrong, or is the video?
Posted on the TSR App. Download from Apple or Google Play
0
reply
RDKGames
Badges: 20
Rep:
?
#2
Report 7 months ago
#2
(Original post by Al4stair)
Hi, please can i have some help with this question:*https://scontent.fbhx2-1.fna.fbcdn.n...58&oe=5CAA49F6



I get this answer (4m):*https://cdn.discordapp.com/attachmen...24/unknown.png



The answer given in the video was just 2m. Am i wrong, or is the video?
2 metres looks good.
0
reply
Al4stair
Badges: 11
Rep:
?
#3
Report Thread starter 7 months ago
#3
(Original post by RDKGames)
2 metres looks good.
But it says from the point O which is at 6m. Don't you need to minus the 2m from the 6m, which is 4m?
Posted on the TSR App. Download from Apple or Google Play
0
reply
RDKGames
Badges: 20
Rep:
?
#4
Report 7 months ago
#4
(Original post by Al4stair)
But it says from the point O which is at 6m. Don't you need to minus the 2m from the 6m, which is 4m?
Don't understand your reasoning.

s tells us the displacement of the particle from O, therefore the answer of 2 means the particle is 2m in the positive direction ahead from O. Meaning it's 2 metres from O.
0
reply
Al4stair
Badges: 11
Rep:
?
#5
Report Thread starter 7 months ago
#5
(Original post by RDKGames)
Don't understand your reasoning.

s tells us the displacement of the particle from O, therefore the answer of 2 means the particle is 2m in the positive direction ahead from O. Meaning it's 2 metres from O.
I do not think so, s=t^3 -7t^2 +8t +6 so when t=0, s=6m. The question asks for the distance from O. If you sub t=2 into the equation you get 2m. Now as I have just shown, O is at 6m. So 6m-2m is 4m. S cannot tell us displacement of the particle from O.
0
reply
RDKGames
Badges: 20
Rep:
?
#6
Report 7 months ago
#6
(Original post by Al4stair)
I do not think so, s=t^3 -7t^2 +8t +6 so when t=0, s=6m. The question asks for the distance from O. If you sub t=2 into the equation you get 2m. Now as I have just shown, O is at 6m. So 6m-2m is 4m. S cannot tell us displacement of the particle from O.
I think I can see what you're saying.

The issue here now lies with the fact that the wording of the question is off. Usually this type of question would read "A particle moves in relation to a fixed point O" (which is typicall notation for the origin of the system) which is when the answer of 2m would make sense, and the video you're referring to has interpreted the question as to mean this.

However if we take O to not be the 'origin' as it usually referred to, and we measure s from the origin then the point O would be 6m ahead of the origin. Indeed, then we would then have that the distance from O is 4m.

The equation s would in either case tell us the displacement of the particle from the origin.
0
reply
God_duck
Badges: 3
Rep:
?
#7
Report 7 months ago
#7
The way I have interpreted this question is when T=0 the particle is 6m away from point O
When t=2 the particle is 2m away from O
Posted on the TSR App. Download from Apple or Google Play
0
reply
Al4stair
Badges: 11
Rep:
?
#8
Report Thread starter 7 months ago
#8
(Original post by RDKGames)
I think I can see what you're saying.

The issue here now lies with the fact that the wording of the question is off. Usually this type of question would read "A particle moves in relation to a fixed point O" (which is typicall notation for the origin of the system) which is when the answer of 2m would make sense, and the video you're referring to has interpreted the question as to mean this.

However if we take O to not be the 'origin' as it usually referred to, and we measure s from the origin then the point O would be 6m ahead of the origin. Indeed, then we would then have that the distance from O is 4m.

The equation s would in either case tell us the displacement of the particle from the origin.
I am confused by what you mean, the particle has moved 4m in relation to the fixed point O, surely. Not sure how that would change the question.
0
reply
RDKGames
Badges: 20
Rep:
?
#9
Report 7 months ago
#9
(Original post by Al4stair)
I am confused by what you mean, the particle has moved 4m in relation to the fixed point O, surely. Not sure how that would change the question.
It would change the question because O would then be the origin and the particle wouldn't be starting on it!
0
reply
Al4stair
Badges: 11
Rep:
?
#10
Report Thread starter 7 months ago
#10
(Original post by RDKGames)
It would change the question because O would then be the origin and the particle wouldn't be starting on it!
The origin would be at 6m. I don't think replacing O with origin would make a difference.
Last edited by Al4stair; 7 months ago
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

  • Norwich University of the Arts
    Postgraduate (MA) Open Day Postgraduate
    Thu, 18 Jul '19
  • Bournemouth University
    Clearing Open Day Undergraduate
    Wed, 31 Jul '19
  • Staffordshire University
    Postgraduate open event - Stoke-on-Trent campus Postgraduate
    Wed, 7 Aug '19

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

Yes, I'll try and go to a uni higher up the league tables (131)
19.35%
Yes, there is a uni that I prefer and I'll fit in better (67)
9.9%
No I am happy with my course choice (383)
56.57%
I'm using Clearing when I have my exam results (96)
14.18%

Watched Threads

View All