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App Mat 1998 Newtons laws

15-06-2007 05:39PM

#1

Shox

Closed Accounts Posts: 78 ✭✭

Join Date: February 2007

Posts: 60

Anyone help, im stumped??

0

Comments

#2 15-06-2007 05:53PM

JC 2K3

Closed Accounts Posts: 7,794 ✭✭✭

Join Date: May 2004

Posts: 7625

Don't bother with it, as Oliver Murphy(guy who wrote the App Maths book) said:

Ugh!Very tricky question because the friction exerted by A on B has an equal but opposite anti-friction which propels A forward!Should never have been asked.It’s a university question.

http://www.discoveringmaths.com/news/belvedere/

I never bothered to solve it at the time. It's not going to come up.

0
#3 15-06-2007 06:35PM

ZorbaTehZ

Registered Users, Registered Users 2 Posts: 2,149 ✭✭✭

Join Date: August 2006

Posts: 2046

Solution

U(BG) Coeffecient of friction between B and ground
U(AB) Coeffecient of friction between A and B

P Force pulling B forward
S Normal Reaction of B

R Normal reaction of A
a acceleration

Equations:
P - [U(BG)].S = 55a
S = R + 35g
R = 20g

If A does not slip, then [U(AB)].R = 20a

SIMULTANEOUS!

P = 35.75g N

EDIT: Typo.

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