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Figure 3 shows a garden gate with a pulley system designed to close the gate - AQA - A-Level Physics - Question 3 - 2022 - Paper 1

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Figure 3 shows a garden gate with a pulley system designed to close the gate. The pulley system raises weight A when the gate is opened. When the gate is released, ... show full transcript

Worked Solution & Example Answer:Figure 3 shows a garden gate with a pulley system designed to close the gate - AQA - A-Level Physics - Question 3 - 2022 - Paper 1

Step 1

Deduce which one of the three materials is used for A.

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Answer

To determine the material used for weight A, we can calculate the volume and density of A and then compare it to the data in Table 2. The volume of A, considering it is a solid cylinder, can be calculated using the formula:

V = ext{area} imes ext{length} = rac{ ext{π} imes (d/2)^2 imes l}{1}

Substituting the values, we find:

  • Diameter (d) = 4.8 × 10⁻² m
  • Length (l) = 0.23 m

Therefore,

V = rac{ ext{π} imes igg( rac{4.8 imes 10^{-2}}{2}igg)^2 imes 0.23}{1} = 1.6 imes 10^{-3} ext{ m}^3

The mass of A can be calculated using the weight of A:

ext{mass} = rac{weight}{g} = rac{35 ext{ N}}{9.81 ext{ m/s}^2} \\ ext{mass} ext{ is approximately } 3.56 ext{ kg}

Now, we calculate the density:

ext{Density} = rac{ ext{mass}}{V} = rac{3.56 ext{ kg}}{1.6 imes 10^{-3} ext{ m}^3} \\ ext{Density} ext{ is approximately } 2.23 imes 10^3 ext{ kg/m}^3

By comparison with Table 2, the calculated density of A closely matches that of concrete, therefore,

A is made of concrete.

Step 2

Calculate the tension in the horizontal cable C when the gate is closed.

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Answer

Given that the tension in rope P is equal to the weight of A, which is 35 N, and that pulley M is negligible, we have:

T=35extNT = 35 ext{ N}

Thus,

The tension in the horizontal cable C when the gate is closed is 35 N.

Step 3

Explain why this increases the tension in the horizontal cable C.

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Answer

As pulley M is pulled to the left, the angle of the rope connected to A increases, which alters the force components acting on cable C. Since the vertical component of the tension must balance with weight A, any increase in the angle increases the horizontal component of the tension within the cable C.

This results in an overall increase in tension as the system responds to maintain equilibrium while A falls or adjusts.

Step 4

Calculate the moment of the tension about the hinge.

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Answer

The moment about the hinge can be calculated using the formula:

extMoment=Timesd ext{Moment} = T imes d

Where:

  • T=41extNT = 41 ext{ N} (tension in cable C)
  • d=0.95extmd = 0.95 ext{ m} (horizontal distance from hinge to point D)

Thus,

extMoment=41extNimes0.95extm=38.95extNm ext{Moment} = 41 ext{ N} imes 0.95 ext{ m} = 38.95 ext{ N m}

So,

The moment of the tension about the hinge is approximately 39 N m.

Step 5

Discuss two independent changes to the design to increase the moment about the hinges due to horizontal cable C.

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Answer

  1. Increase the Length of Cable C: One way to increase the moment is to extend the horizontal cable C further away from the hinge. This increases the distance at which the tension acts, thereby increasing the moment.

  2. Enhance the Stiffness of the System: Another potential design change is to reinforce the hinges of the gate, making it able to withstand greater tensions without deformation. This may allow for higher operational tension in cable C, thus increasing the resulting moment about the hinge.

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