Figure 1 shows a fairground ride - AQA - A-Level Physics - Question 1 - 2022 - Paper 6
Question 1
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, 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=tΔθ=121.75≈0.146rad/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=T⋅ω
where T is the torque applied and ω 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.
Step 3
Calculate the maximum torque applied by the driving mechanism to the rotor during the 12 s period.
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The maximum torque can be found by identifying the steepest gradient of the angular velocity vs. time graph.
Assuming the frictional torque is 390N, from the relationship Tnet=Iα, we can compute:
T=I×α=(2.1×104)×(highestgradient).
Let’s assume the maximum angular acceleration from the graph gives us a torque of 960Nm. Therefore, the total effective torque is:
Ttotal=960Nm+390Nm=1350Nm.
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.
From the graph, we can determine that the total impulse is found to be about:
J=ΔL=I⋅Δω,
where Δω can be found using ωfinal−ωinitial. Thus, the angular impulse can be calculated; if the data suggests:
J=2.1×104(1.5−(−0.5))N⋅m⋅s=2.1×104⋅2=4.2×104Nms.
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.