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A light uniform rigid bar is pivoted at its centre - AQA - A-Level Physics - Question 18 - 2017 - Paper 1
Question 18
A light uniform rigid bar is pivoted at its centre. Forces act on the bar at its ends and at the centre. Which diagram shows the bar in equilibrium? A B C D
Worked Solution & Example Answer:A light uniform rigid bar is pivoted at its centre - AQA - A-Level Physics - Question 18 - 2017 - Paper 1
Step 1
Which diagram shows the bar in equilibrium?
Answer
To determine which diagram shows the bar in equilibrium, we must analyze the moments acting on the bar. The condition for equilibrium is that the sum of the clockwise moments must equal the sum of the counterclockwise moments.
In this scenario:
- Diagram A has unequal forces that will not balance each other out, resulting in a net moment.
- Diagram B has an 8 N force at one end and an uneven placement of other forces which will not balance.
- Diagram C presents forces acting on both ends (2 N and 4 N) and at the center (4 N) which creates balanced moments, maintaining equilibrium.
- Diagram D also shows forces that lead to an unbalanced moment.
Thus, the correct diagram that shows the bar in equilibrium is:
C.