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 Form 4 Physics Uniform Circular Motion Questions and Answers

a).Define angular velocity.
b).Three masses are placed on a rotating table at distances 6cm, 9cm and 12 cm respectively from the centre of rotation. When the frequency of rotation is varied it is noted that each mass slides off at a different frequency of rotation of the table. Table 1 below shows the frequency at which each mass slides off.
i).State two factors that determine the frequency at which each mass slides off.
ii).Oil is now poured on the table before placing the masses .Explain the effect of this on the frequency at which each mass slides off.
c).Figure 12 below shows a fly wheel of radius 14cm suspended about a horizontal axis through its Centre so that it can rotate freely about the axis. A thread is wrapped round the wheel and a mass attached to its loose end so as to hang at a point 1.2m above the ground. When the mass is released, it accelerates at 0.28m/s2.Determine the angular
velocity of the wheel just before the mass strikes the ground.

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Answer Text:
a).Angular velocity is the rate of change of angular displacement with time.
-Friction force
ii).The oil will reduce the friction force which provides the centripetal force,the frequency of sliding off is lowered.
c).#V^2=u^2 +2as = 0 + 2 times 0.28 times 1.26#.
#v =sqrt 0.7056 = 0.84 = romega rightarrow 0.84 = 0.14 times omega rightarrow# w =6 rad /sec.