Why it is easy to move the wheel chairs than normal chairs
Answers
Its a long explanation
Case (1) moving a wheel on rough surface (real life )
A) When we move a wheel we usually do pure rolling . Means rolling without slipping .
B) why friction acts ? Friction's life ambition is to prevent relative motion btwn two surface and the moment the relative motion is zero our friction stops acting .
Friction sees that ground is at rest now it checks the bottom point of the wheel which is in contact of ground . We know that during pure rolling the bottom point is at rest wrt ground (google it how) . so the ground and the bottom point both are at rest . There is no need of friction force .
Case 2 our chair
Chair in motion ground at rest . Friction activated . It will tryto bring the chair to res .( at the same time friction tries to move the ground forward )
So in case of rolling a wheel no opposition by friction and pushing a chair we face the opposition of friction .
( If friction force doesnt act during rolling then why does wheel stops after sometime . Ponder it .)