motion question (1 Viewer)

matchalolz

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Q7b
http://imgur.com/7EBOEIg,nTnWuKn#0
what does confined in a mathematical context mean?

Q10bii
http://imgur.com/7EBOEIg,nTnWuKn#1
I just don't get how to do this in general

Q11a
http://imgur.com/ltPRiSN

I'm having trouble finding the value of k, like I got a value but the answers say otherwise
idk, can someone point out the mistake/s in my working/reasoning

firstly, I thought it was weird how they said integrate because I thought you weren't allowed to directly integrate in 3u motion, as everything is expressed in displacement

but i integrated anyways:
a = -k
v = -k + C

then i assumed that the start of the runway was x=0, and v=100 at this point
100 = -k(0) + C
therefore C = 100
v = -kx + 100

then i thought that it stopped moving 2km later, so x=2000m and v=0
0 = -2000k + 100
2000k = 100
k = 1/20

I'm finding that I'm struggling a lot through this topic and i don't know how to improve because I keep trying to do questions but I can't do them (which demotivates me even further)
I'm considering dropping down to 2u but idk coz it has motion as well D:
 

Librah

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Q7b
http://imgur.com/7EBOEIg,nTnWuKn#0
what does confined in a mathematical context mean?

Q10bii
http://imgur.com/7EBOEIg,nTnWuKn#1
I just don't get how to do this in general

Q11a
http://imgur.com/ltPRiSN

I'm having trouble finding the value of k, like I got a value but the answers say otherwise
idk, can someone point out the mistake/s in my working/reasoning

firstly, I thought it was weird how they said integrate because I thought you weren't allowed to directly integrate in 3u motion, as everything is expressed in displacement

but i integrated anyways:
a = -k
v = -k + C

then i assumed that the start of the runway was x=0, and v=100 at this point
100 = -k(0) + C
therefore C = 100
v = -kx + 100

then i thought that it stopped moving 2km later, so x=2000m and v=0
0 = -2000k + 100
2000k = 100
k = 1/20

I'm finding that I'm struggling a lot through this topic and i don't know how to improve because I keep trying to do questions but I can't do them (which demotivates me even further)
I'm considering dropping down to 2u but idk coz it has motion as well D:
Confined in interval just means within the extremes of motion (largest displacements).

For your other questions, use (d/dx) (v^2/2)=a, you can derive that fairly easily. a=dv/dt by definition and (dv/dx)(dx/dt)=vdv/dx
 
Last edited:

matchalolz

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Confined in interval just means within the extremes of motion (largest displacements).

For your other questions, use (d/dx) (v^2/2)=a, you can derive that fairly easily. a=dv/dt by definition and (dv/dx)(dx/dt)=vdv/dx
thanks for trying to help but I'm just really lost actually. I know you're meant to start with this and if I were smart enough to have gone from here maybe i wouldn't be posting? see my logic yeah?

but BUMP
 

InteGrand

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thanks for trying to help but I'm just really lost actually. I know you're meant to start with this and if I were smart enough to have gone from here maybe i wouldn't be posting? see my logic yeah?

but BUMP
For example, here's how to do Q.10:











 
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