[SOLVED] Newton's Laws of Motion

BabyMilo · #1 $Old$ November 6th, 2009, 12:54 PM

Quote:

A particle P of mass 8 kg rests on a smooth plane inclined at 30 degrees to the horizontal. It is connected by a light inextensible string passing over a smooth light pulley at the top of the plane, to a particle of mass 3kg which is on a smooth plane inclined at 60 degrees to the horizontal.

Find the acceleration of the system and the tension in the string.

What I did is

Code:

 T-8a=8gsin30

Code:

 3a-T=3gsin60

Used the calculator for simultaneous equation, which is not the answer in the back of the book. It should be 1.249m/s^2 and 29.21N. But i've got -64.25 and -12.9

many thanks for your help!

BabyMilo · #2 $Old$ November 6th, 2009, 01:04 PM

Found the answer.
Wasted so much time typing =.=""
In my second equation

Code:

 3a-T=3gsin60

should be

Code:

 3a+T=3gsin60