Page 26 - SP015 Past Years PSPM Chapter 6 -14 Ver 2020

PHYSICS PSPM SEM 1 1999 - 2017

PSPM 2013/2014 SF016/2 No. 5(c)

42.

32 cm
4000 rpm
6 cm

FIGURE 8.20

FIGURE 8.20 shows a 2.76 kg solid disc of diameter 32 cm with a 2.66 kg solid
cylindrical axle of diameter 6 cm. The moment of inertia of the hollow disc is
2
1 M (R  R 2 ) where R 1 is the radius of solid disc and R 2 is the radius of cylindrical
2 disc 1 2
2
1
axle. The moment of inertia of the cylinder is M cylinder R . Calculate the
2
2

(a) moment of inertia of the system about the axis of the cylindrical axle. [2 m]

(b) energy required to rotate the system about the axis from an angular speed of
1000 rpm to 4000 rpm. [3 m]

PSPM 2013/2014 SF016/2 No. 5(d)

43. A solid sphere and a solid cylinder from rest roll without slipping down a slope from
the same height. Both of them have the same mass and radius.

Given the moment of inertia of the solid sphere and solid cylinder are 2 5 MR and
2
2
1 MR respectively, which one of them will reach the bottom of the slope first? Justify
2
your answer.
[3 m]

PSPM 2014/2015 SF016/2 No. 4(b)

44. Two ice skaters, each of mass 60 kg hold hands and spin in a circle with a period of
4.3 s. The distance between them is 1.44 m.

(a) Calculate the angular velocity. [1 m]

(b) Calculate the centripetal acceleration. [1 m]

(c) Calculate the pulling force that acts on each hand. [1 m]

(d) Describe their subsequent motion after they separate. [1 m]

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