(i) If you take a chair and tilt it such that it makes an angle theta with the ground, will pushing the chair be easier or pulling?

(ii) If you take the same chair and don't

tilt it, will pushing be easier or pulling?

Asked by kalpanasingh.ito | 16th Feb, 2020, 07:25: PM

Expert Answer:

Left side figure shows the forces acting on a tilted chair.    F is applied force to move the chair.
W is weight acting at the centre of mass, N are reaction forces by floor and μN are friction forces.
If we move the tilted chair by pushing,  the applied force will be slightly upward .
Hence reaction force is reduced by vertical component Fv , reaction force is given by N = W - Fv
If the tilted chair is pulled , applied force will be downward , hence vertical component of applied force will be
added to W to get reaction force . Hence while pulling the tilted chair reaction force by floor is greater compare
to the reaction force given by floor while pushing the tilted chair
Since friction force is proportional to reaction force and pushing force to tilted chair gives less reaction force,
pushing a tilted chair is easier than pulling.
Right side figure shows the forces acting on the chair resting on horizontal floor.
If the resting chair is moved by pulling, applied force will be upward.
As explained above, reaction force is reduced by vertical component of applied force.
Hence pulling the chair will be easier than pushing

Answered by Thiyagarajan K | 17th Feb, 2020, 11:09: AM

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