# NCERT Physics Class 11 Exemplar Ch 3 Motion In A Straight Line Part 3

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Q. 14 Give examples of a one-dimensional motion where

(a) the particle moving along positive x-direction comes to rest periodically and moves forward.

(b) the particle moving along positive x-direction comes to rest periodically and moves backward

Q. 15 Give example of a motion where at a particular instant.

Answer: are suitably chosen positive constants.

Q. 16 An object falling through a fluid is observed to have acceleration given by a = g – bv where g = gravitational acceleration and b is constant. After a long time of release, it is observed to fall with constant speed. What must be the value of constant speed?

Q. 17 A ball is dropped and its displacement vs time graph is as shown Figur (displacement x is from ground and all quantities are upwards).

(a) Plot qualitatively velocity vs time graph.

(b) Plot qualitatively acceleration vs time graph

The ball is released and is falling under gravity. Acceleration is –g , except for the short time intervals in which the ball collides with ground, and when the impulsive force acts and produces a large acceleration.

Q. 18 A particle executes the motion described by

(a) Where does the particle start and with what velocity?

(b) Find maximum and minimum values Show thatand increase with time anddecreases with time.