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

Answer:

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?

Answer:

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

Plot qualitatively velocity, acceleration graph

Plot Qualitatively Velocity, Acceleration Graph

Answer:

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.

Image of falling under gravity

Image of Falling under Gravity

Image of falling under gravity

Image of Falling under Gravity

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.

Answer:

Q. 19 A bird is tossing (flying to and fro) between two cars moving towards each other on a straight road. One car has a speed of while the other has the speed of . The bird starts moving from first car towards the other and is moving with the speed of and when the two cars were separted by . What is the total distance covered by the bird? What is the total displacement of the bird?

Answer: Relative speed of cars = , time required to meet

Thus, distance covered by the bird

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