One end of a horizontal uniform beam of weight and length is hinged on a vertical wall at point and its other end is supported by a light inextensible rope. The other end of the rope is fixed at point , at a height above the hinge at point . A block of weight is attached at the point of the beam, as shown in the figure (not to scale). The rope can sustain a maximum tension of . Which of the following statement(s) is(are) correct?
Answers: A. The vertical component of reaction force at does not depend on · B. The horizontal component of reaction force at is equal to for · D. The rope breaks if
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Written solution
Step 1: Determine the angle of the rope.
Since and , the triangle is a right-angled isosceles triangle.
Step 2: Resolve the tension force into components.
The horizontal and vertical components of the tension acting at point are determined by the angle.
Step 3: Apply rotational equilibrium about the hinge .
The sum of the torques about point must equal zero.
Step 4: Find the horizontal reaction force at the hinge.
From horizontal translational equilibrium, the horizontal reaction force equals the horizontal component of tension.
Step 5: Find the vertical reaction force at the hinge.
From vertical translational equilibrium, the sum of vertical forces must equal zero.
Step 6: Analyze Statement 1.
The vertical component of the reaction force at is independent of .
Since does not depend on , this statement is correct.
Step 7: Analyze Statement 2.
The horizontal component of the reaction force at is when .
This statement is correct.
Step 8: Analyze Statement 3.
The tension in the rope is when .
Since , this statement is incorrect.
Step 9: Analyze Statement 4.
The rope breaks if given the maximum tension .
Since tension increases with , the rope breaks for , making this statement correct.
Answer: Statements (1), (2), and (4) are correct.