Author Topic: Mechanics Question  (Read 6783 times)

nid404

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Re: Mechanics Question
« Reply #15 on: October 15, 2010, 01:56:23 pm »


Where does the 6cos60 come from :(
OMGGGG I DONT GETTT IT.

brain has shutdown.



6cos60 is the same as 6sin30

elemis

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Re: Mechanics Question
« Reply #16 on: October 15, 2010, 02:21:46 pm »
The 6 N force makes an angle of 60 degrees with the y axis. I used this 60 degrees when resolving in the Y DIRECTION.

Offline Dania

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Re: Mechanics Question
« Reply #17 on: October 15, 2010, 02:50:53 pm »
Asif :)

I keep getting a tension of 8.32N when in fact I need to get 3N. I think I'm resolving the forces incorrectly, can someone please draw it out for me, and solve the question.


:)

nid404

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Re: Mechanics Question
« Reply #18 on: October 15, 2010, 03:12:22 pm »
10 mins

nid404

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Re: Mechanics Question
« Reply #19 on: October 15, 2010, 03:27:20 pm »
attached


elemis

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Re: Mechanics Question
« Reply #20 on: October 15, 2010, 03:29:52 pm »
6cos60 is the same as 6sin30

Yeah, I prefer using cosine instead of sine. I'm biased that way :P

nid404

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Re: Mechanics Question
« Reply #21 on: October 15, 2010, 03:30:47 pm »
Yeah, I prefer using cosine instead of sine. I'm biased that way :P

Racist :P

elemis

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Re: Mechanics Question
« Reply #22 on: October 15, 2010, 03:36:27 pm »

Offline Deadly_king

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Re: Mechanics Question
« Reply #23 on: October 15, 2010, 03:37:48 pm »
attached



Quite long but good ;)

You could have resolved the weight P along the line of the string PS. But first you need to find the angles of the triangle APS.

T = 5cos 53.1 = 3.0N :)

Am sure this method will make Ari happy :P

nid404

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Re: Mechanics Question
« Reply #24 on: October 15, 2010, 03:41:12 pm »
hahaha :P

yup deadly king, that's one way to go abt it  :)

elemis

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Re: Mechanics Question
« Reply #25 on: October 15, 2010, 03:49:47 pm »
Am sure this method will make Ari happy :P

This wasnt my question smarty pants ::)

Offline Deadly_king

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Re: Mechanics Question
« Reply #26 on: October 15, 2010, 04:06:09 pm »
hahaha :P

yup deadly king, that's one way to go abt it  :)
Hats off to you though.....you were faster since you started earlier :P

@ Ari : I know .......but I used cosine and that's what you prefer, right?

Offline Dania

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Re: Mechanics Question
« Reply #27 on: October 16, 2010, 01:06:38 pm »
Refer to the attachment, thanks :)
:)

nid404

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Re: Mechanics Question
« Reply #28 on: October 16, 2010, 01:35:57 pm »
in the first part you found v=5m/s

for the second part, acceleration, t seconds after passing through A is given by (10-3t)
at t=0, v=5m/s

v=10t-0.15t2+C

substituting t=0 and v=5

you get c=+5

Offline Dania

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Re: Mechanics Question
« Reply #29 on: October 16, 2010, 11:45:27 pm »
A ball is projected from a point O on the edge of a vertical cliff. The horizontal and vertically upward components of the initial velocity are 7ms-1 and 21ms-1 respectively. At the time t seconds after the projection the ball is at the point (x,y) referred to horizontal and vertically upward axes through O. Air resistance may be neglected.

(i) Express x and y in terms of t, and hence show that y= 3x- 0.1x2

The ball hits the sea at a point which is 25m below the level of O.

(ii) Find the horizontal distance between the cliff and the point where the ball hits the sea.


:)