Page 27 - SP015 Past Years PSPM Chapter 6 -14 Ver 2020

PSPM SP015

PSPM 2015/2016 SF016/2 No. 5(b)

45. A 15 N m torque acts on a grinding wheel after the power is switched off. Given the
2
angular velocity of the wheel is 1200 rpm and its moment of inertia is 0.8 kg m ,
calculate the time for the wheel to stop. [3 m]

PSPM 2016/2017 SF016/2 No. 5(b)

2
46. A flywheel with moment of inertia 8 kg m is acted upon by a constant torque of
50 N m. Calculate the

(a) angular acceleration. [1 m]

-1
(b) time for it to rotate from rest to 70 rad s . [1 m]

-1
(c) power when the angular velocity is 50 rad s . [1 m]

PSPM 2017/2018 SF016/2 No. 5(c)

47.

1.5 m

F = 0.8 N

FIGURE 8.21

FIGURE 8.21 shows a 0.75 kg airplane model is attached by an arm rod of negligible
mass flies in horizontal circle 1.5 m in radius. The airplane model acts a force of 0.8 N
perpendicular to the rod. By assuming the airplane as a point mass, calculate the

(a) torque about the axis passing through the centre of the circle. [2 m]

(b) angular acceleration of the airplane. [2 m]

(c) linear acceleration of the airplane tangent to its flight path. [2 m]

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