A 1.0 kg ball and a 2.0 kg ball are connected by a 1.0-m-long rigid, massless rod. The rod is rotating cw about its center of mass at 20 rpm. What torque will bring the balls to a halt in 5.0 s? Answer in Nm.

ringearV

ringearV

Answered question

2020-10-26

A 1.0 kg ball and a 2.0 kg ball are connected by a 1.0-m-long rigid, massless rod. The rod is rotating cw about its center of mass at 20 rpm. What torque will bring the balls to a halt in 5.0 s? Answer in Nm.

Answer & Explanation

Ezra Herbert

Ezra Herbert

Skilled2020-10-27Added 99 answers

Given
m1=1kg and m2=2kg
Distance between them is 1metre.
x=m1x1+m2x2m1+m2
x=10+211+2=23=0.67m
Moment of inertia is
I=m1x12+m2x22=1(0.67)2+2(0.332)2
I=0.4489+0.2178=0.6667=0.67kgm2.
As per Angular Impulse
τ×t=L1L2
τ=L10t
τ=I1ω1t
τ=0.6723.140.335=0.28Nm
ω=20r±=2060=0.33rps

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