In a circular motion? A) particle cannot have uniform motion B) particle cannot have uniformly accelerated motion C)particle cannot have net force equal to zero D)particle cannot have any force in tangential direction

The question has multiple answers. Please give reasons while you select your answers.

Answer 1

A, B (and C - almost always)

The direction of motion keeps on changing - hence A

The direction of the acceleration keeps on changing (even when the speed is uniform the acceleration, though constant in magnitude. is always towards the center - its direction keeps changing) - hence B

Since the acceleration keeps on changing - the net force must keep on changing - and can never be zero throughout. However, consider a body fixed to a point by a rod of length #l# so that it can travel in a vertical circle. If it has just the right speed (#sqrt{4gl}#) at its lowest point, it will just make it to the top, where it will be instantaneously stationary. At that point (and at that point only) the net force acting on it (the sum of gravity acting downwards and the rod pushing upwards ) will be zero.

If the particle is in uniform circular motion, i.e. if it moves at a uniform speed, it will have no tangential force. If the speed changes, it has a tangential acceleration - and has a tangential force.

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Answer from HIX Tutor

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.