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can u draw components indicate +and -
Have you learned about FBD?
i am always getting T-Mg cos 60 =Ma
what is FBD
Free body diagram.
So the next step is to isolate the object and put all forces that are applied TO the body.
Memorizing formulas is dangerous, because sometimes theta can refer to something else.
i did not memorize i drew FBD
something wrong with vectors
|dw:1358006741723:dw| Do you have something like this?
^ what i have
According your your FBD, "T-Mg cos 60 =Ma" is not correct.
i mean T-Mg sin 60
That's good. Can you continue?
yes i can but i am getting acceleration as -
this is other half
-T+mg sin 30 =Ma
M is 5kg for both find the acceleration
|dw:1358007244777:dw| So you have two unknowns (T and a) and two equations. :)
ok so i got mgsin 30-mgsin 60=ma+ma
m=5kg for both i got a=-1.830 which is wrong
i must get a=1.830
Your equation assumed that the masses accelerate DOWN the 30 deg. plane, so a<0 is correct! :)
It is logical that the masses slide down the 60 deg. plane. So put mg sin(60)-T = ma , and T-mg sin(30) = ma This assumes mgsin(60)>T (=> a>0) and T>mg sin(30) , again => a>0
so what ur doing is making accelration + right
You don't always have to guess the direction right the first time. Make a reasonable guess, using logic, and if it comes out negative, reexamine to see if it is logical, or if you made a mistake. This is how scientiests work: examine the work when there is a surprise.