Question

3. A particle has a velocity u towards east at t = 0. Its
acceleration is towards west and is constant. Let xa and
xo be the magnitude of displacements in the first 10
seconds and the next 10 seconds
(a) XA < XB (b) xa = xp (C) xa > XB
(d) the information is insufficient to decide the relation
of XA with XB.

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Answer 1

The correct option is (C) xa > Xb

• Displacement magnitude depends on initial velocity, time Length, and acceleration. Only time is known in this case while magnitude of initial velocity and acceleration is unknown.

• Particulate speed u to the east  and acceleration is to the west. As acceleration is the other way round, acceleration is negative
• v = u + at  where a is -ve, thus v will keep decreasing
• S = ut + (1/2)at², where time is 10 seconds, thus V at 10 sec < V at 0 sec
• So Displacement in 1st 10 sec will be more than next 10 sec, so Xa > Xb