How much left of course? (1 Viewer)

gabn

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I got one more lesson, and then i'm done. motion around a banked surface is what we are doing next lesson.

and we are finished ext. 1 and maths so it's just study and going back to things we don't know.
 

mojako

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you will finish the course, but probably harder 3U wont be properly taught :p
Ive finished everything except harder 3U
and ive finished all of the 3U course.
 

CrashOveride

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Circular motion currently. Then graphing still to go and harder 3u. Have to come back on holidays to do harder 3u :/

We finisihed 3u course.

Also, while i am here, i think answer to this question is wrong:

A model plane of mass 5kg attached to the end of an inelastic wire of length 20m flies in a horizontal circle of elevation 30degrees, while the other end of the wire is held fixed. If the lift force L acts at right angles to the wire and L is twice the weight of the plane, find the speed of the plane in m/s.

I can show tension T = 71,7N ..then I go from Tsin60 = mv^2 /r. By trig, r = 10sqrt(3).
Re-arranging, and i get v = 14.7m/s. But answer at the back has like 19.6m/s.
 

mojako

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CrashOveride said:
Circular motion currently. Then graphing still to go and harder 3u. Have to come back on holidays to do harder 3u :/

We finisihed 3u course.

Also, while i am here, i think answer to this question is wrong:

A model plane of mass 5kg attached to the end of an inelastic wire of length 20m flies in a horizontal circle of elevation 30degrees, while the other end of the wire is held fixed. If the lift force L acts at right angles to the wire and L is twice the weight of the plane, find the speed of the plane in m/s.

I can show tension T = 71,7N ..then I go from Tsin60 = mv^2 /r. By trig, r = 10sqrt(3).
Re-arranging, and i get v = 14.7m/s. But answer at the back has like 19.6m/s.
oh no.. asking question in the wrong place :p
what's the "elevation"? u mean the circle is not horizontal?
does the question have a picture to confirm?

ur school is so mean, haha..
 

CrashOveride

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Like if you look up 30degrees, thats your point P say. Draw a 'circle' (ellipse) and connect that point on the ground , say O, to P and to the other side of the circle opposite P. Is that clearer ?

My school is not mean, it's just heavily under resourced :)
 

mojako

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yes it does.. took me a while to realise that the wire is tied to the ground though.. (needed to examine ur answer to conclude that).. I was thinking of conical pendulum type object

with ur question, the book is correct.
mv^2 / r = Tsin60 + 49
where 49 is the horizontal component of force L.
 

Dabbu

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Actually, apparantly we did the harder X1 during the X1 course so we are covered for that (and the rest of the X1 class is able to answer the hard question at the end).

My teacher said that we should just finish in time and have a day spare! (muck up day all the way!)

Cheers
 

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