A point starts moving in a straight line with a certain acceleration. At a time t after beginning of motion the acceleration suddenly becomes retardation of the same value. The time in which the point returns to the initial point is
(4) Cannot be predicted unless acceleration is given
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(2) In this problem point starts moving with uniform acceleration a and after time t (Position B) the direction of acceleration get reversed i.e. the retardation of same value works on the point. Due to this velocity of points goes on decreasing and at position C its velocity becomes zero. Now the direction of motion of point reversed and it moves from C to A under the effect of acceleration a.
We have to calculate the total time in this motion. Starting velocity at position A is equal to zero.
Velocity at position B ⇒ v = at [As u = 0]
Distance between A and B,
As same amount of retardation works on a point and it comes to rest therefore
∴ and time required to cover this distance is also equal to t.
∴ Total time taken for motion between A and C = 2t
Now for the return journey from C to A
Hence total time in which point returns to initial point