1) A turning moment diagram (TMD) graphically represents torque over crank angle and is used to calculate work done per cycle and mean torque. 2) A flywheel stores excess energy from the engine during the power stroke and releases it during other strokes to reduce fluctuations in speed. There are disc and rim types of flywheels. 3) To calculate the energy stored in a flywheel, formulas use mass, radius of gyration, angular velocity, and the coefficient of fluctuation of speed. The problem gives values for an engine to calculate the required flywheel's mass moment of inertia.