GabbytheGreek_48
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#1
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#1
hey maths people i know this is kinda early but im terrible at mechanics especially these three topics:
Application vectors
Newtons laws with vectors
Projectiles
so was wondering if anybody whose doing mechanics and good at it could help me with these and mayb i can help some other people with the same problem or different topics thanks

idk if its a glitch but pressed maths and wont come in maths
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problemq
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#2
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#2
Post any specific problems you are struggling with and you'll get help.
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GabbytheGreek_48
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#3
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#3
At time 0900, a snowmobile passes a fixed origin O with constant velocity (8i-14j) kmh-1, where i and j are unit vectors due east and due north respectively. An hour and a half later, the snowmobile changes velocity so that it is travelling due west with speed 20kmh-1.

a) at what time is the snowmobile due south of O?

help with these times of questions and general mechanics tips for these topics would be good sorry for asking so much but I dont want mechanics to bring me down especially if they have questions like these that are phrased differently
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GabbytheGreek_48
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#4
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#4
thanks again for the help
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Steelmeat
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#5
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#5
(Original post by GabbytheGreek_48)
At time 0900, a snowmobile passes a fixed origin O with constant velocity (8i-14j) kmh-1, where i and j are unit vectors due east and due north respectively. An hour and a half later, the snowmobile changes velocity so that it is travelling due west with speed 20kmh-1.

a) at what time is the snowmobile due south of O?

help with these times of questions and general mechanics tips for these topics would be good sorry for asking so much but I dont want mechanics to bring me down especially if they have questions like these that are phrased differently
Zacken
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Zacken
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#6
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#6
(Original post by GabbytheGreek_48)
At time 0900, a snowmobile passes a fixed origin O with constant velocity (8i-14j) kmh-1, where i and j are unit vectors due east and due north respectively. An hour and a half later, the snowmobile changes velocity so that it is travelling due west with speed 20kmh-1.

a) at what time is the snowmobile due south of O?

help with these times of questions and general mechanics tips for these topics would be good sorry for asking so much but I dont want mechanics to bring me down especially if they have questions like these that are phrased differently
What specific bit confuses you?

At time 09:00, let's call this our original position. Using displacement = speed * time we have our position vector at any time t as

(0, 0) + t (8, -14).

We want our position 1 and a half hours later. That's (0, 0) + 1.5 (8, -14).

Simplify that.

Travelling due west with speed 20 kmh^-1 is the same as saying it has a constant velocity of (-20, 0). But it's starting at 1.5(8, -14).

So its position at a general time t is 1.5(8, 14) + t(-20, 0).

What does it mean for the thing to be due south of O, it means that it's 'i' component is 0, right? Draw a graph and label a point right underneath the origin, what is the i component of that?

So you have the i component as 1.5(8) - 20t which can set to 0 and solve.
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GabbytheGreek_48
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#7
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#7
(Original post by Zacken)
What specific bit confuses you?

At time 09:00, let's call this our original position. Using displacement = speed * time we have our position vector at any time t as

(0, 0) + t (8, -14).

We want our position 1 and a half hours later. That's (0, 0) + 1.5 (8, -14).

Simplify that.

Travelling due west with speed 20 kmh^-1 is the same as saying it has a constant velocity of (-20, 0). But it's starting at 1.5(8, -14).

So its position at a general time t is 1.5(8, 14) + t(-20, 0).

What does it mean for the thing to be due south of O, it means that it's 'i' component is 0, right? Draw a graph and label a point right underneath the origin, what is the i component of that?

So you have the i component as 1.5(8) - 20t which can set to 0 and solve.
oh wow thanks alot that really clears things up and generally i get lost in these type of questions either that or i try something and its not the right answer this helps alot i might have more questions hope i dont get annoying thanks alot
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Middriver
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#8
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#8
(Original post by Zacken)
What specific bit confuses you?

At time 09:00, let's call this our original position. Using displacement = speed * time we have our position vector at any time t as

(0, 0) + t (8, -14).

We want our position 1 and a half hours later. That's (0, 0) + 1.5 (8, -14).

Simplify that.

Travelling due west with speed 20 kmh^-1 is the same as saying it has a constant velocity of (-20, 0). But it's starting at 1.5(8, -14).

So its position at a general time t is 1.5(8, 14) + t(-20, 0).

What does it mean for the thing to be due south of O, it means that it's 'i' component is 0, right? Draw a graph and label a point right underneath the origin, what is the i component of that?

So you have the i component as 1.5(8) - 20t which can set to 0 and solve.
Name:  image.jpg
Views: 236
Size:  489.2 KB Is that right? Got a little confused.
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Zacken
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#9
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#9
(Original post by GabbytheGreek_48)
oh wow thanks alot that really clears things up and generally i get lost in these type of questions either that or i try something and its not the right answer this helps alot i might have more questions hope i dont get annoying thanks alot
Don't worry about it, a lot of this is just trying to lay your working out in logical steps.
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Zacken
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#10
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#10
(Original post by Middriver)
Name:  image.jpg
Views: 236
Size:  489.2 KB Is that right? Got a little confused.
Yeah, that's correct. It wants the time though, so what's 9 o'clock + 2.1 hours?

Hint: it's 11 o'clock + (0.1 * 60) minutes.
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GabbytheGreek_48
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#11
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#11
(Original post by Zacken)
Yeah, that's correct. It wants the time though, so what's 9 o'clock + 2.1 hours?

Hint: it's 11 o'clock + (0.1 * 60) minutes.
so 9 + 2 hours and six mins? so 1106
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Zacken
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#12
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#12
(Original post by GabbytheGreek_48)
so 9 + 2 hours and six mins? so 1106
Sounds right, yeah.
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GabbytheGreek_48
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#13
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#13
(Original post by Zacken)
Sounds right, yeah.
ok i think im getting the topic more because ive been doing the questions(slowly but still) and getting the right answers
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Zacken
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#14
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#14
(Original post by GabbytheGreek_48)
ok i think im getting the topic more because ive been doing the questions(slowly but still) and getting the right answers
Awesome.
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GabbytheGreek_48
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#15
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#15
(Original post by Zacken)
Awesome.
thans again i might have mre questions though cus im going through the other topics etc
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Zacken
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#16
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#16
(Original post by GabbytheGreek_48)
thans again i might have mre questions though cus im going through the other topics etc
Feel free to use the maths forum whenever.
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