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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. Figure 2 shows the angular velocity $\omega$ of the rotor with time $t$ during a 12 s period. 0 1.1 Determine the mean angular ve... 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 determine the mean angular velocity ωˉ\bar{\omega} over the 12 s period, we can calculate the total angular displacement Δθ\Delta \theta and divide it by the total time interval.\n\nFrom the graph, we observe the angular velocity ω\omega at different intervals. The total area under the curve can be computed as the sum of areas of the trapezoids and rectangles formed. For this case:\n\nΔθ=(2.0×1.5)+(3.0×1)+(5.0×1.0)+(5.0×1.0)=3.5 rad\Delta \theta = (2.0 \times 1.5) + (3.0 \times 1) + (5.0 \times -1.0) + (5.0 \times 1.0) = 3.5 \text{ rad}\n\nNow, considering that the total time is 12 s, we have:\n\nωˉ=ΔθΔt=3.512=0.2917rads1\bar{\omega} = \frac{\Delta \theta}{\Delta t} = \frac{3.5}{12} = 0.2917 \, rad \, s^{-1}\n\nThus, the mean angular velocity is approximately 0.29 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

From the equation for power output, we have: P=TωP = T \cdot \omega.\n\nDuring the first 2 seconds (from the graph), the maximum angular velocity ω\omega is approximately 1.5 rad/s. The net torque can be found from the maximum torque exerted during this period, calculated from the graph. Assuming a net torque of 960 N m:\n\nP=Tω=960Nm1.5rad/s=1440WP = T \cdot \omega = 960 \, N \, m \cdot 1.5 \, rad/s = 1440 \, W\n\nSo, the power output is 1440 W.

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 TmaxT_{max} can be identified from the graph by examining the steepest gradient during the first phase.\n\nHere, we find that during the initial segment of the torque, the maximum torque occurs at the slope around 2.0 seconds. Given that the angular velocity is maximized at this point, the torque value is about 960 N m.\n\nThus, the maximum torque during this period is 960 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 JJ can be computed from the integral of torque over the time interval.\n\nBetween t=2.0st = 2.0 \, s and t=7.0st = 7.0 \, s, the torque remains relatively constant and will be taken as its average. Assuming an average torque (based on the graph) of around 480 N m over the 5-second period:\n\nJ=t1t2TdtTavg(t2t1)=480Nm(7.02.0)=2400NmsJ = \int_{t_1}^{t_2} T \, dt \approx T_{avg} \cdot (t_2 - t_1) = 480 \, N \, m \cdot (7.0 - 2.0) = 2400 \, N \, m \, s\n\nThis results in an angular impulse of 2400 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 torque characteristics observed in the angular velocity graph, the graph representing the variation of torque is the first one. Therefore, the correct choice is to tick the appropriate box corresponding to the first graph.

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