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The diagram shows the forces acting on a uniform rod - AQA - A-Level Physics - Question 20 - 2020 - Paper 1
Question 20
The diagram shows the forces acting on a uniform rod. 20 N 0.20 m 0.30 m 6 N 10 N 4 N Which statement is correct? A The rod is in equilibrium. B For equi... show full transcript
Worked Solution & Example Answer:The diagram shows the forces acting on a uniform rod - AQA - A-Level Physics - Question 20 - 2020 - Paper 1
Step 1
A The rod is in equilibrium.
Answer
To determine if the rod is in equilibrium, we need to assess if the sum of the moments around any point equals zero and if the resultant force is zero. Here, the rod experiences downward forces (20 N, 6 N, 10 N, 4 N) which are not equal to the opposing upward force. Hence, this statement is incorrect.
Step 2
B For equilibrium, an anticlockwise moment of 1.0 N m is needed.
Answer
Calculating moments: the clockwise moment created by the 10 N force acting 0.20 m from the pivot equals 10 N * 0.20 m = 2.0 N m. This far exceeds the anticlockwise moment provided by the 6 N force acting 0.30 m from the pivot (6 N * 0.30 m = 1.8 N m). Therefore, this statement is also incorrect.
Step 3
C For equilibrium, a clockwise moment of 1.0 N m is needed.
Answer
Using the same moment calculations, the rod needs an additional clockwise moment to balance the forces. Since the net moment already favors clockwise and exceeds 1.0 N m, this statement is true. The section already has sufficient clockwise moment.
Step 4
D For equilibrium, the 10 N force should be increased to 20 N.
Answer
Increasing the 10 N force would lead to a larger total downward force while not contributing effectively to reducing the moment imbalance. The forces acting upon the rod would remain unbalanced, contradicting equilibrium possibilities. Thus, this statement is incorrect.