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another physics problem?
A 2.00 kg aluminum block and a 6.00kg copper block are connected by a light string over a frictionless pulley. the two blocks are allowed to move on a fixed steel block wedge ( of angle O=30.0 degrees). making use of table 4.2, determine:
(a) the acceleration of the two blocks and (b) the tension in the string
table 4.2
Coefficients of friction
Steel on steel: us 0.74, uk 0.57
aluminum on steel: us 0.61, uk 0.47
copper on steel: us 0.53. uk 0.36
**Please note the "u" are the funny little cursive ones, I dont know what they are called..
ok intuitively the heavier block is going to slide down, while the lighter block slides up. since the question asks for acceleration, we are going to assume it wont sit static on the surface. .
the light block has a weight (massxgravity) of 2x9.8=19.6N
the total force normal (perpendicular) to the surface of the block is a function of the angle, =19.6xcos30 = 16.97
the drag due to friction = normal force x uk = 16.97x0.47= 7.98N
for the heavy block,
mg = 6x9.8 =58.8
Fnorm = 58.8xcos30 = 50.92
drag=50.92x0.36= 18.33N
so now the sum of forces along the surface of the block.
trying to move the small block down is 19.6xsin30= 9.8N, and in the same direction is its drag, 7.98N
Trying to move the large block is 58.8xsin30= 29.4, and opposing it is it's drag, 18.33N.
so
+29.4 -18.33 -9.8N -7.98 = less than 0
oops. it looks like my initial assumption was wrong and there is not enough gravitational force to overcome friction. we used u kinetic, and u static would give even higher friction forces.
so acceleration = 0
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