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A builder is making a path using uniform rectangular stones - Edexcel - A-Level Physics - Question 13 - 2023 - Paper 1
Question 13
A builder is making a path using uniform rectangular stones. A stone is resting horizontally on a step and is held in equilibrium by the builder's foot. The centre o... show full transcript
Worked Solution & Example Answer:A builder is making a path using uniform rectangular stones - Edexcel - A-Level Physics - Question 13 - 2023 - Paper 1
Step 1
State what is meant by equilibrium.
Answer
Equilibrium occurs when all the forces acting on an object are balanced, resulting in a state of rest or uniform motion. For a stone to be in equilibrium, the downward gravitational force and any upward forces must be equal, and the torques about any point must also sum to zero.
Step 2
State what is meant by the centre of gravity of an object.
Answer
The centre of gravity of an object is the point at which the weight of the object is evenly distributed in all directions. It is the pivot point for torque calculations and represents the average position of the weight of the object.
Step 3
The position and direction of P are shown on the diagram below.
Answer
The forces acting on the stone include:
- The weight of the stone acting downwards at its centre of gravity.
- The reaction force from the step acting upwards.
- The force P applied at the edge of the stone, directed horizontally.
Step 4
Calculate the magnitude of P.
Answer
To find the magnitude of P, we must consider the moments (torques) about the edge of the step where the stone rests.
- Weight of the stone, W = 415 N, is acting at a distance of 0.45 m (half the length of the stone) from the edge of the step.
- The force P acts at a distance of 0.50 m from the step.
Setting the clockwise moments equal to the counterclockwise moments gives:
Calculating:
Thus, the magnitude of P is approximately 373.5 N.