Author Topic: All Mechanics DOUBTS HERE!!! (Read 96404 times)

iluvme · « **Reply #420 on:** April 17, 2011, 01:18:49 pm »

Quote from: ~~!$!HUSH!$!~~ on April 17, 2011, 12:55:21 pm

MJ 2003 Q4 part 2,i did it wrong and then the mark scheme had 2 dots above x,anyone can help me with this

CIE?

HUSH1994 · « **Reply #421 on:** April 17, 2011, 02:46:46 pm »

yes please

iluvme · « **Reply #422 on:** April 17, 2011, 06:14:15 pm »

Two dots above x is d²x/dt²

Here you go,

HUSH1994 · « **Reply #423 on:** April 19, 2011, 04:51:40 pm »

Thanks alot,+rep

RoRo · « **Reply #424 on:** April 20, 2011, 11:46:14 am »

Q. A particle is projected vertically upwards from a point A with speed u ms-1. The particle takes 2 6/7 to reach its greatest height above A. Find
a) the value of u
Ans is 28
b) the total time for which the particle is more than 17 1/2m above A.
Ans is 4 2/7

My question is, when doing part b) I get 2 answers 5 and 5/7, why do we subtract them to get 4 2/7?

astarmathsandphysics · « **Reply #425 on:** April 25, 2011, 03:28:25 pm »

The particle rises above 17 1/2 m at t=5/7 and falls below 17 1/2 m at t=5 so is above 17 1/2 m for 5-2/7 =4 2/7 s

RoRo · « **Reply #426 on:** April 25, 2011, 08:36:49 pm »

Quote from: astarmathsandphysics on April 25, 2011, 03:28:25 pm

The particle rises above 17 1/2 m at t=5/7 and falls below 17 1/2 m at t=5 so is above 17 1/2 m for 5-2/7 =4 2/7 s

Ohh, okay, thank you!

Can you please answer my questions in my previous post here? I uploaded a picture with a couple of questions that I needed help on, thanks a lot!

astarmathsandphysics · « **Reply #427 on:** April 25, 2011, 09:05:04 pm »

Will do them in bed and post in morning

astarmathsandphysics · « **Reply #428 on:** April 25, 2011, 10:56:34 pm »

Here
did yo use 30 or 60?

astarmathsandphysics · « **Reply #429 on:** April 26, 2011, 01:48:34 pm »

those questions answered in attachments

RoRo · « **Reply #430 on:** April 29, 2011, 09:21:12 am »

Quote from: astarmathsandphysics on April 26, 2011, 01:48:34 pm

those questions answered in attachments

Thank you very much for your help Sir, I'll go through them once I start revising Mechanics again, because right now I've got my A2 math mocks coming up next week!

doubtigetastar · « **Reply #431 on:** April 29, 2011, 09:02:14 pm »

Guys i need ur help in this :
a uniform lamina ABCDEF is formed by removing a rectangle of dimensions 8 cm and 12 cm from a square of side length 20 cm , find the distance of the centre of mass of the lamina from its edges : a) AF b) FE

i made a diagram it's in the attachments .

astarmathsandphysics · « **Reply #432 on:** April 29, 2011, 10:28:23 pm »

As soon As OS installs

astarmathsandphysics · « **Reply #433 on:** April 30, 2011, 07:53:00 am »

Attachment uploadedfrom my phone

doubtigetastar · « **Reply #434 on:** April 30, 2011, 11:24:27 am »

Thank you very much +REP.
one last question , how did you get the distance of the big rectangle (area 400) from the line FE

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