IIT JEE , AIEEE Forum - Physics , Mechanics

sinjan.j

look carefully:

in my textbook it says that "a body is said to be in a state of motion if it changes its position with respect to the surroundings in a given time."

now, i understand the fact that motion is totally related to the surroundings.

but what i donot understand is that why is the part "in a given time" included in the statement.

don't u think that it is irrelevant? if u think that it is relevant then please tell me how.

please reply fast. I WOULD REALLY WANT TO BUILD MY BASICS UP.

thanx in advance.

swatygupta

suppose a body is moving such that its velocity changes from time to time.. then sometimes its moving and sometimes it may not...

u will be able to define motion only at a certain point of time..

"in a given time" is inappropriate, it should be "at a given time".

srujana

Dear sinjan,

I think here we take time as a reference frame.
Hence we determine the change in the position as the time passes.Hence the part 'in a given time' is relevant here.
Thus if a body changes its position with the time it is said to in motion. But if t=0, or if s=0, then the body is taken to be at rest

rakesh61

Swaty has done it perfect

vineetgupta_17

this sentence implies that the body is in motion for only the time it is changing its position with respect to its surrounding.

chakradarraju

motion means change in position
initial position different from the final position
a body cannot be in the initial and final position at the same time.
so, at each instant of time the body will occupy a position.

SHATABDI

DEAR SINJAN ,

WHOEVER THINKS THAT T=0 HAS A WRONG CONCEPT. THE TIME FACTOR INFLUENCES THE MOTION OF A BODY 2 A GREAT EXTENT.

E.g- A BODY TRAVELS A DIST 4RM S_{1^{(INITIAL .P) TO S}2^{(FINAL.P) DURING TIME INTERVAL OF T}1^{TO T}2 ^SECS.}

_{^{THE DIST TRAVERSED DUE TO MOTION OF AN OBJECT CHANGES W.R.T TIME.}}

_{^{HENCE IT IS VERY IMPORTANT TO NOTE THAT TIME CAN NEVER BE EQUAL TO O SECS}}

sankydreams

in a given time is wrong (which buk r u reading?)
i can prove it
suppose a body is moving in a circular path and spose it completes one revolution in time t
after first revolution and time = t, the displacement of body = 0
but this doesnt imply that it is not in motion

i think that even at a given time is also not correct
as if we talk about an instant, then we can assume the body at rest and its position doesnt change with its surroundings at that instant
so we can say that at that instant, body is at rest

i dont think time plays a role here in this definition

plz correct if i m wrong
rate if u agree with me...

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