The hour hand and the minute hand of a clock are 2.7m long and 4.5m long and have masses of 60kg and 100kg respectively. Calculate the total rotational kinetic energy of the two hands about the axis of rotation.(adsbygoogle = window.adsbygoogle || []).push({});

[tex]w=circumfrence/time=2rpi/t=2(2.7m)pi/86400s[/tex]

[tex]w=1.96x10^{-4}rad/s[/tex]

[tex]w=circumfrence/time=2rpi/t=2(4.5m)pi/3600s [/tex]

[tex]w=0.00785rad/s[/tex]

[tex]energy=[m_1r_1^2w_1^2]+[m_2r_2^2w_2^2][/tex]

[tex]energy=[60kg*(2.7m)^2*(1.96x10^{-4}rad/s)^2]+[100kg*(4.5m)^2*(0.00785rad/s)^2][/tex]

[tex]energy=0.1248J[/tex]

is this the total energy of the two hands?

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# Homework Help: Clock hand's rotation

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