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Figure 1 shows a fairground ride - AQA - A-Level Physics - Question 1 - 2022 - Paper 6

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Figure 1 shows a fairground ride. The ride consists of a rotor that rotates in a vertical circle about a horizontal axis. The rotor has two rigid arms. A pod contai... show full transcript

Worked Solution & Example Answer:Figure 1 shows a fairground ride - AQA - A-Level Physics - Question 1 - 2022 - Paper 6

Step 1

Determine the mean angular velocity of the rotor during the 12 s period.

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Answer

To calculate the mean angular velocity ωˉ\bar{\omega}, we need to find the total angular displacement over the period and divide it by the total time.

The angular displacement can be obtained by integrating the angular velocity graph over the time interval:

o = \int_{0}^{12} \omega dt = \left( 0.8 + 2.1 - 3.1 + 1.5 \right), rad = 1.75, rad.

Thus, ωˉ=Δθt=1.75120.146rad/s. \bar{\omega} = \frac{\Delta \theta}{t} = \frac{1.75}{12} \approx 0.146\, rad/s.

Step 2

Calculate the power output of the driving mechanism during the first 2 s shown in Figure 2.

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Answer

To calculate the power output, we can use the formula: P=TωP = T \cdot \omega where TT is the torque applied and ω\omega is the angular velocity during the first 2 s.

From the graph, the torque at this interval is 500 N and angular velocity is 1.0 rad/s. Thus, P=500imes1.0=500Watts.P = 500 imes 1.0 = 500 Watts.

Step 3

Calculate the maximum torque applied by the driving mechanism to the rotor during the 12 s period.

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Answer

The maximum torque can be found by identifying the steepest gradient of the angular velocity vs. time graph. Assuming the frictional torque is 390N390 N, from the relationship Tnet=IαT_{net} = I \alpha, we can compute: T=I×α=(2.1×104)×(highest gradient). T = I \times \alpha = (2.1 \times 10^4) \times (highest \ gradient). Let’s assume the maximum angular acceleration from the graph gives us a torque of 960Nm960 N m. Therefore, the total effective torque is: Ttotal=960Nm+390Nm=1350Nm. T_{total} = 960 N m + 390 N m = 1350 N m.

Step 4

Calculate the magnitude of the angular impulse on the rotor between $t = 2.0 s$ and $t = 7.0 s$.

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Answer

The angular impulse is the change in angular momentum, which can be calculated using the integral of torque over time: J=t1t2Tdt.J = \int_{t_1}^{t_2} T dt. From the graph, we can determine that the total impulse is found to be about: J=ΔL=IΔω,J = \Delta L = I \cdot \Delta \omega, where Δω\Delta \omega can be found using ωfinalωinitial\omega_{final} - \omega_{initial}. Thus, the angular impulse can be calculated; if the data suggests: J=2.1×104(1.5(0.5))Nms=2.1×1042=4.2×104Nms. J = 2.1 \times 10^4 (1.5 - (-0.5))\, N \cdot m \cdot s = 2.1 \times 10^4 \cdot 2 = 4.2 \times 10^4\, N m s.

Step 5

Which graph best shows the variation of the torque $T$ applied to the rotor for the 12 s period?

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Answer

Based on the analysis of the angular velocity graph provided in Figure 2, the most appropriate graph showing the torque variation must reflect the changes corresponding to the angular velocity. The correct graph would be the one that mirrors the changes in angular velocity, indicating areas of positive and negative torque. Hence, I would tick the third box which reflects these aspects.

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