Block A has mass of mA = 58kg and rests on a flat surface. The coefficient of static friction between the block and the surface
is 0.300. The coefficient of static friction between the rop and the fixed peg B is 0.310. The width of the block is d = 0.290m. Find the greatest mass, mC, that weight C can have such that block A does not move.
1 answer:
Answer:
The greatest mass, that the weight C can have such that block A does not move is approximately 23.259 kg
Explanation:
The given parameters are;
The mass of the block A= 58 kg
The coefficient of static friction between the block and the surface, = 0.300
The coefficient of static friction between the rope and the fixed peg, B = 0.310
Let T represent the tension in the rope
Therefore, when the rope is static, T = The normal reaction at the peg, B,
The angle of inclination of the rope holding the block A = arctan(3/4) ≈ 36.87°
The length of the rope = √(0.4² + 0.3²) = 0.5
∴ sin(θ) = 3/5 = 0.6
cos(θ) = 4/5 = 0.8
The vertical component of the tension in the rope = T × sin(θ) = 0.6·T
The horizontal component of the tension in the rope = T × cos(θ) = 0.8·T
The friction force = μ×(W - 0.6·T) = 0.300×(58×9.8 - 0.6·T) = 170.52 - 0.18·T
The block will start to move when we have;
The horizontal component of the tension in the rope = The friction force
∴ 0.8·T = 170.52 - 0.18·T
0.8·T + 0.18·T = 170.52
0.98·T = 170.52
T = 170.52/0.98 = 174
Therefore, the tension in the rope = T = 174 N = The normal reaction at the peg, B
The frictional force at the peg, =
×
= 0.310 × 174 N = 53.94 N
The weight of the mass, ,
= The frictional force at the peg,
+ The tension in the rope
∴ The weight of the mass, ,
= 53.94 N + 174 N = 227.94 N
Weight, W = Mass, m × The acceleration due to gravity, g, from which we have;
m = W/g
Where;
g = 9.8 m/s²
∴ =
/g = 227.94 N/(9.8 m/s²) ≈ 23.259 kg.
The greatest mass, that the weight C can have such that block A does not move = ≈ 23.259 kg.
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