Need a Double Check / Verification

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In the following diagram there is a coefficient of friction, μ, of 0.15 between the 5.0 kg mass and the surface. Calculate the tension in the cable connecting the two masses and the resulting acceleration.

FBD
Physics Question 3 U1-C.gif


m1= 2 kg
m2= 5 kg
μ= .15
g= 9.8 m/s2

Equation 1 ~

Fg - FT = FN

2kg × 9.8m/s2 - 2kg(a) = FT

Equation 2 ~

Fg = FN = 5kg (9.8 m/s2)
~ μFN = .15(49) = 7.35 N

FT - FF = ma

FT = 5kg(a) + 7.35

~Set Equations Equal to Each Other~

19.6 - 2a = 5a - 7.35

26.95 = 7a

a = 3.85 m/s2

Sub into Eq to get FT on String

2 (9.8) - 2(3.85) = FT

FT = 11.9 N
 
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Inferior Mind said:
In the following diagram there is a coefficient of friction, μ, of 0.15 between the 5.0 kg mass and the surface. Calculate the tension in the cable connecting the two masses and the resulting acceleration.

FBD
View attachment 55355

m1= 2 kg
m2= 5 kg
μ= .15
g= 9.8 m/s2

Equation 1 ~

Fg - FT = FN

2kg × 9.8m/s2 - 2kg(a) = FT

Equation 2 ~

Fg = FN = 5kg (9.8 m/s2)
~ μFN = .15(49) = 7.35 N

FT - FF = ma

FT = 5kg(a) + 7.35

~Set Equations Equal to Each Other~

19.6 - 2a = 5a - 7.35

26.95 = 7a

a = 3.85 m/s2

Sub into Eq to get FT on String

2 (9.8) - 2(3.85) = FT

FT = 11.9 N

Look Good !
 
No, it isn't smart guy.

5a + 7.35 =/= 5a - 7.35