Asked in ETEA MDCAT 2005 2005Moderate

One hollow and one solid cylinder of the same radius are rolling down an inclined plane. Which of them will reach the end of the plane first?

Correct answer: A. Solid cylinder

  • A. Solid cylinder
  • B. Hollow cylinder
  • C. Both simultaneously
  • D. Depends upon the behavior among them

Explanation

mgcos∅ will get balanced by the normal force For rolling without slipping (pure rolling), we have a = àR ... (1) I am using symbol à for angular acceleration Two forces are acting, f and mgsin∅ submission of F =ma mg sin∅ -f= ma ... (2) (Here f is the friction force, a = linear acceleration à = angular acceleration) As we know, T= là (T=torque, I=inertia) from eqn(1)....à=a/R T=I(a/R) We know torque equals force into the radius But we also know the force of friction and radius are also perpendicular so T = f×R f×R = I ( a/R ) f =I ( a/R² ).......(3) From eqn (2) and (3), mgsin∅ - I ( a/R² ) =ma a = (mgsin∅) / (1/R²+m) a = (mgR²sin∅) / I+mR² m, R and ∅ are constant So, a is proportional to 1/I (I=inertia) The body whose inertia will less reach the bottom first We know, Inertia of solid cylinder = ½ mR² Inertia of hollow cylinder= ½ m ( R2² +R1²) I (solid) < I (hollow) So solid cylinder will have greater acceleration So, it will reach the end first

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