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A turning moment diagram is a graph showing the variation of torque produced by an engine or motor with the angle of rotation of the output shaft - AQA - A-Level Physics - Question 2 - 2019 - Paper 6
Question 2
A turning moment diagram is a graph showing the variation of torque produced by an engine or motor with the angle of rotation of the output shaft. Figure 2 shows th... show full transcript
Worked Solution & Example Answer:A turning moment diagram is a graph showing the variation of torque produced by an engine or motor with the angle of rotation of the output shaft - AQA - A-Level Physics - Question 2 - 2019 - Paper 6
Step 1
0.2-1 State what is represented by the area between the curve and the angle axis for a turning moment diagram.
Answer
The area between the curve and the angle axis in a turning moment diagram represents the work done or energy output over one complete cycle of motion. This area essentially quantifies the amount of torque produced by the motor or engine at various angles of rotation, highlighting the efficiency and performance characteristics of the machine.
Step 2
0.2-2 Discuss why, to drive this machine, the diesel engine would need to be fitted with a flywheel. In your answer you should explain why the electric motor does not require a flywheel.
Answer
Why the electric motor does not require a flywheel
Electric motors deliver smooth and continuous torque, allowing for constant rotation without major fluctuations in output, which makes a flywheel unnecessary. The design of electric motors inherently allows them to manage varying loads without losing performance.
Why the torque of the diesel engine varies over one cycle
In contrast, the torque output of a diesel engine dramatically fluctuates throughout each cycle of operation, with periods of high torque (power stroke) and periods where the torque momentarily drops to zero (exhaust and intake strokes). This variation is due to the internal combustion process, where the expansion and contraction of gases produce changes in pressure and torque output.
How the moment of inertia of the flywheel influences the motion of the output shaft
A flywheel serves to smooth out these torque fluctuations by storing rotational energy during the high torque phase and releasing it during lower torque phases. The moment of inertia (M) of the flywheel affects how easily it can maintain rotational motion. A larger moment of inertia allows the flywheel to store more energy, hence providing a more stable output to the load, ensuring that the machine receives a more constant torque despite the inherent variations in diesel engine performance.