PPH0046 MECHANICS TRIMESTER 1 2023/2024 (2310) Problem 1: Scenario 1: A circular grinding disk of diameter 50 cm and mass 400 kg is spun by an electric motor to rotate at high speed. When the motor is turned off and the speedometer is recording a constant reading of 100 rev/min. When an axe is pressed against the rim of the disk, as shown in Figure P1S1, it is found that the speedometer reading drops to 80 rev/min in 2.0 s. The rotational that inertia, I, of the grinding disk is 1 mR, where m and R are the mass and radius of the disk respectively. 2 a) Find the net force that causes the drop in the speed of the disk. What type of force that contributed to this net force? b) How far the axe has been grinded in this 2.0 s? c) If this net force were to be constantly and continuously applied, how much longer the disk would be moving until it stopped? d) The motor is turned on when the operator noticed that the speedometer reading dropped to 80 rev/min. With the axe still being grinded, how long it takes for the motor to spin the disk back to the speed of 100 rev/min? The motor has a stated constant torque of 16 N.m for a range of speed up to 300 rev/min. e) What would the answer in d) be if the axe is taken away? R e Figure P1S1 (20 marks)