Force and Motion with two unknows

[ankitp3]

Body A in Fig. 6-36 weighs 100 N, and body B weighs 77 N. The coefficients of friction between A and the incline are μs = 0.52 and μk = 0.28. Angle θ is 31°. Let the positive direction of an x-axis be down the slope. What is the acceleration of A if A is initially (a) at rest, (b) moving up the incline, and (c) moving down the incline?
http://edugen.wiley.com/edugen/courses/crs1650/art/qb/qu/c06/fig06_34.gif

=S m stuck @ -FT + mgsintheta = ma and i am stuck with two unknowns.. Tension and acceleration

 

[tiny-tim]

Welcome to PF!

-FT + mgsintheta = ma and i am stuck with two unknowns.. Tension and acceleration

Hi ankitp3! Welcome to PF!

Yes, you do have two unknowns.. tension and acceleration …

but you also have two equations, one for body A and one for body B.

 

[ankitp3]

still having hard time solving this problem :S

 

[tiny-tim]

still having hard time solving this problem :S

ok, show us your two equations, and we'll see what we can do …

 

[ankitp3]

FK + mgsingtheta - FT = m1ax (block A)

Ft - Fg = m2gy (block b)

ukmgcostheta - mgsintheta - FT = m1ax

Ft - (wB) = (wB/9.8)a

ukmgcostheta + mgsintheta - Ft (< sub in Ft from the last equation)

 

[tiny-tim]

FK + mgsingtheta - FT = m1ax (block A)

Ft - Fg = m2gy (block b)

ukmgcostheta - mgsintheta - FT = m1ax

Ft - (wB) = (wB/9.8)a

ukmgcostheta + mgsintheta - Ft (< sub in Ft from the last equation)

Sorry … I've stared at this for several minutes and I can't follow it.

Can you put the numbers in?