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posted by  jenna.111 on 7/3/2009 11:08:22 PM  |  status: Live  |  Earned Karma: 0

Acceleration

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Two blocks (5.0 kg and 6.0 kg) are connected through a frictionless system. Find the tension in the string and the acceleration of the system. The angle of the ramp is 45o.
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posted by Great King on 7/4/2009 12:14:10 AM  |  status: Live
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This question is bit not quite clear,cos' we don't know whether the block 5 kg or 6 kg is resting on the ramp or not. Let's assume the 5 kg block rests on the ramp.
Consider the 6-kg block hangs by a string passing over a frictionless pulley.
By using Newton's 2nd law, ΣF = ma  Mg - T = Ma 60 - T = 6 a  .... (1)
Consider the 5 kg block rest on the ramp:
Using Newton's 2nd law, T - 50 sin(45) = 5a   ..... (2)
Solving (1) and (2), then we have
 and T = 46.6 N
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posted by jenna.111 on 7/4/2009 12:22:11 AM  |  status: Live
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ramp and pulley system

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posted by Anonymous on 7/4/2009 1:50:09 AM  |  status: Live
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Response Details:
Fnet=ma
Resolve vector forces into component forces x and y with y perpendicular to surface and x paralell to surface.
mass 1 = 6kg
mass 2 = 5kg
g=9.8m/s2
Θ =45degrees
Forces for Mass 1
m1g=(6kg)(9.8m/s2)=58.8N
F1,x=(mg)sin θ = (58.8)sin 45 =41.58N since the object is falling the sign is negative thus,
F1,x = -41.5N This force is also equal to Tension T since it is pulling on mass 2 as they are both in freefall on a frictionless surface.
Forces for Mass 2
F2,x=(mg)sin θ = (49)sin 45 =34.65N since the object is falling the sign is negative thus,
F2,x= -34.65N
using 2nd Law: Fnet = Max where M is total mass(m1+m2) and ax is acceleration along the surface.
Fnet,x = Max
F1,x+F2,x =Max
-41.58-34.65N=(11)ax
-76.23N=(11)ax
-76.23N
You can check that each mass has the same acceleration along the surface by  applying F=ma to each mass:
F1,x / m1 =ax
F2,x / m2 = ax
 as you would expect because both object are in freefall their component accelerations are equal to each other and to:
(g) Sin 45 = (9.8)Sin 45= 6.93m/s2.
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