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## Newton, Find T

 Quote by SherBear Could this finally be correct? T = (15kg)(9.80m/s^2)(sin30)-31.825N / (15kg) (12kg) T= .637 N ?
i'm confused

you had T - m1gsin30° - 31.825 = m1a

and m2g - T = m2a

to find T, you need to eliminate a, so multiply the first equation by m2 and the second equation by m1, and then subtract

 Quote by tiny-tim i'm confused you had T - m1gsin30° - 31.825 = m1a and m2g - T = m2a to find T, you need to eliminate a, so multiply the first equation by m2 and the second equation by m1, and then subtract
Sorry Tim =/

T=m1g sin 30° - 31.825 (m2)

T=(15 kg) (9.80 m/s^2) (sin 30°) - 31.825 (12 kg)

T=1382.1 N?

Then...2nd Equation

T = m2g (m1)

T=(12 kg) (9.80 m/s^2) (15 kg)

T=1764 N?

Then Subtract the 2....

1764 - 1382.1 = 381.9 N

T= 381.9 N?
 Here's a different way, can you tell me if it's right or wrong? forces on A u*m*g*Cos30 -T = ma T - 0.25*15*9.8*cos30 = 15*a T - 31.82N = 15a .........................................i Forces on B m*g-T = ma 12*9.8 -T = 12a 117.6-T = 12a...........................................ii adding i and ii -31.82 + 117.6 = 27a 85.78 = 27a a = 3.17 m/s/s Now T = 117.6 - 12*9.8 = 0 No motion
 So any input? I still don't know if I'm doing this right.

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 Quote by SherBear Here's a different way, can you tell me if it's right or wrong? forces on A u*m*g*Cos30 -T = ma T - 0.25*15*9.8*cos30 = 15*a T - 31.82N = 15a .........................................i Forces on B m*g-T = ma 12*9.8 -T = 12a 117.6-T = 12a...........................................ii adding i and ii -31.82 + 117.6 = 27a 85.78 = 27a a = 3.17 m/s/s Now T = 117.6 - 12*9.8 = 0 No motion
yes, that's the right method, but in A you've missed out the m1gsin30°

(alternatively, if you only want T and not a, then you could eliminate a instead of T )
 I don't like that way, could I also find Acceleration and knowing both masses I could rewrite: the sum of F=m2g-T=m2a as T= m2g / m2a = 12(9.8) / 12 (.454 assuming the acceleration i computed is correct) = 21.58 N T=21.58 N ?
 Or for box b use sum of F=T m2g so T=m2g.....12(9.8 m/s^2) = 117.6N ?
 Which T is the same all the way through because it's 1 rope?