A solid metallic sphere of mass and radius is free to roll (without sliding) over the inclined surface of a wooden wedge of equal mass . Wedge lies on a smooth horizontal floor. When the system is released from rest, find the ratio , here is the friction between the sphere and the wedge.
The wedge is a right triangle
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The force m a 1 acting on the sphere is a pseudo force.
The equations governing the motion of the sphere and wedge are:
m g + N 2 cos θ + f sin θ = N 1 … ( 1 ) N 2 sin θ − f cos θ = m a 1 … ( 2 ) m g cos θ = N 2 + m a 1 sin θ … ( 3 ) m a 1 cos θ + m g sin θ − f = m a 2 … ( 4 ) f R = ( 5 2 m R 2 ) α … ( 5 ) a 2 = R α … ( 6 )
Equation 1 balances forces along the vertical for the wedge.
Equation 2 is the application of Newton's 2nd law for the wedge along the horizontal.
Equation 3 is a force balance in a direction perpendicular to the incline for the sphere.
Equation 4 is the application of Newton's 2nd law for the sphere along the incline.
Equation 5 is the torque equation τ = I α about the COM of the sphere.
Equation 6 is the pure rolling constraint.
Taking cos 3 7 o = 0 . 8 and solving the six equations in six unknowns gives:
f = 9 2 m g N 2 = 3 2 m g
The resultant force between the wedge and the sphere is:
F = f 2 + N 2 2
Apologies for the messy diagram. I have denoted f as the friction force between the sphere and the wedge.