A barbell with two equal masses 2.5 kg on either end rotates about an axis perpe

Question

A barbell with two equal masses 2.5 kg on either end rotates about an axis perpendicular to the bar with an angular velocity of 0.56 rad/s. If one of the masses is 0.23 m away from the axis of rotation and the entire system has a rotational kinetic energy of 14.5 J, how far away is the other mass from thay axis in metres
Note: Treat the weights on the barbell as point masses, so that you can use I = mr^2 A barbell with two equal masses 2.5 kg on either end rotates about an axis perpendicular to the bar with an angular velocity of 0.56 rad/s. If one of the masses is 0.23 m away from the axis of rotation and the entire system has a rotational kinetic energy of 14.5 J, how far away is the other mass from thay axis in metres
Note: Treat the weights on the barbell as point masses, so that you can use I = mr^2
Note: Treat the weights on the barbell as point masses, so that you can use I = mr^2

Explanation / Answer

m1 = m2 = 2.5kg

angular velocity = w = 0.56 rad/sec

r1 = 0.23m

rotational kineticenergy = 14.5 joules

(1/2)*I*w^2 = 14.5

(1/2)*(m1*r1^2 + m2*r2^2)*w^2 = 14.5

(1/2)*(2.5*0.23^2 + 2.5*r2^2)*0.56^2 = 14.5

r2 = 6.1 m ..................

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