00:01
In this problem of motion along a straight line we have given that the position function xt, this is position function xt of a particle moving along x -axis is, say x is equals to 4 .0 minus 6 .0 t square where x is measured in meters and t is measured in seconds.
00:25
Now it is asked that at what time and where does the particle momentarily? it stops.
00:34
So this particle would stop when the velocity is equal to 0.
00:37
So dv, that is here dx divided with d t.
00:41
So here v is equal to dx divide with t would be equal to zero.
00:46
So for this we have to differentiate it.
00:48
Now when we differentiate it, so this value would be minus 12.
00:52
So this is minus 12 multiplied with t.
00:59
That means particle momentarily stops when minus 12 multiplied with t is equal to 0 that means at t is equal to 0 this particle momentarily it stops so at say time t is equal to 0 second it is stops and it is at the origin now this would be not at origin because when we put t is equal to 0 the position would be 4 .0 so we can say at 4 .0 meters and now it is asked that at what positive and negative time the particle pass through origin so first we have to tell the negative time and then in part d we have to tell the positive so for this we have to put x is equals to 0 by putting x is equal to 0 so this value would be 4 .0 minus 6 .0 t 2 .0 2 .2 so 2 is so t is square is equal to 4 divided with 6 that is 2 divided with 3 now t is equal to under root 2 divided with 3 3.
02:13
This is equals to here t is equals to plus and minus 0 .816 second...