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Introduction to motion - class-IX

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The motion of an ant on a floor along the edges is an example of translatory motion.

  1. True

  2. False


Correct Option: A
Explanation:

The given statement is true that the motion of an ant on the floor along the edges is an example of translatory motion.

Smoke particles from a chimney exhibit :

  1. Random or irregular motion

  2. Circular motion only

  3. Linear motion only

  4. Rotational motion only


Correct Option: A
Explanation:

Smoke particles from the chimney have velocities in different direction and thus they exhibit random or irregular motion.

Name the type : A flying insect

  1. Random motion (Irregular motion)

  2. Circular motion

  3. Rolling motion

  4. Purely translation motion 


Correct Option: A
Explanation:

A flying insect is an example of random motion (irregular motion).

Rectilinear motion is a motion that occurs in :

  1. Straight line

  2. Plane

  3. Both A and B

  4. None


Correct Option: A
Explanation:

The rectilinear motion is a straight line motion or one dimensional motion.

The process of change in position of an object over time is called

  1. rest

  2. stationary

  3. motion

  4. none of the above


Correct Option: C
Explanation:

A body is said to be in motion if it changes its position over time.

What we say when a body remains in one position for a long time?

  1. Motion

  2. Rest

  3. Stationary

  4. None of the above


Correct Option: B
Explanation:

A body is said to be at rest if it remains in one position for a long time.

Which type of motion of an object that moves in a straight line?

  1. Rectilinear motion

  2. Periodic motion

  3. Circular motion

  4. None of the above


Correct Option: A
Explanation:
Rectilinear motion is an another name for straight line motion.
Ex. A train moving on a track.

What is common to the following?
Motion of the propeller of a flying helicopter, the minute hand of a watch, the tape of cassette recorder.

  1. All are example of translatory motion

  2. All are examples of oscillatory motion

  3. All are examples of rotatory motion

  4. All are examples of periodic motion


Correct Option: C
Explanation:

Motions of the propeller of a flying helicopter, the minute hand of watch and tape of cassette recorder are the example of rotatory motion.
Correct answer is option C.

The motion in which all points of a moving body move uniformly in the same line or direction is known as 
  1. Rolling

  2. Rotatory

  3. Both A and B

  4. Translational


Correct Option: D
Explanation:
If a body rotates its motion its rotatory. Rolling motion is combination of rotation and translation motion.
Only in translational motion body moves along a straight line, that means body doesn't rotate then its motion is translational.

Which type of motion of an object that moves at a fixed distance from a fixed point?

  1. Periodic motion

  2. Rectilinear motion

  3. Circular motion

  4. None of the above


Correct Option: C
Explanation:

Circular motion is the motion of an object that moves at a fixed distance from a fixed point. Here all objects rotate in circular motion.

If an object moves along a straight path it is said to be ____ or ____ motion. Fill in the blank.

  1. Linear

  2. one dimensional

  3. two dimensional

  4. both A and B


Correct Option: D
Explanation:

Linear motion (also called rectilinear motion) is one dimensional motion along straight line.

Which of the following is a type of motion?

  1. Circular

  2. Rectilinear

  3. Periodic

  4. All of the above


Correct Option: D
Explanation:
'A body is said to be in motion, if it changes its position with respect to its surrounding.'
Example;-Circular motion;"The motion of an object in a circular path is known as circular motion"
Linear motion-"(also called rectilinear motion) is one dimensional motion along straight line"
Periodic motion-Motion repeated in equal intervals of time

If a coin is tossed by a boy in a moving train and it falls behind him, then the motion of the train is

  1. Uniform

  2. Accelerated

  3. Retarded

  4. Along a circular track


Correct Option: B
Explanation:

If the train was moving with uniform velocity, then the coil would have fallen at the same place from where it was tossed up. 

When the train is accelerating it changes its speed (increases),on the other hand the coin still moves with the same speed as before .So when the coin is tossed, by the time the coin reaches back, the train would have moved ahead and so the coin will fall behind the spot from where it was tossed.

A person, seated in a train under motion, is at rest with reference to :

  1. The train.

  2. A person watching him from the front seat.

  3. A car moving opposite to the train.

  4. Trees on the ground.


Correct Option: A,B
Explanation:

When a man seats in a train, he is rest with respect to the train and with respect to another train or car which is moving opposite with same velocity of the first train.

In a race, boy A sees another boy B overtaking him at a speed $v$. If they were running in opposite directions, speed of B as seen by A is   

  1. $=v$

  2. $<v$

  3. $>v$

  4. $\geq v$


Correct Option: C
Explanation:

When they are running in same direction, $v = v _B - v _A$

When they are running in opposite directions, $v' = v _B + v _A > v$

A police inspector in a jeep is chasing a pickpocket an a straight road. The jeep going at its maximum speed v (assumed uniform). The pickpocket rides on the motor-cycle of a waiting friend when the jeep is at a distance d away, and the motorcycle starts with a constant acceleration a. The pick pocket will be caught if  

  1. $v\, \geq\, \sqrt{2ad}$

  2. $v^2\, \geq\, \sqrt{2ad}$

  3. $v\, \geq\, \sqrt{3ad}$

  4. $v\, \geq\, \sqrt{2ad^2}$


Correct Option: A
Explanation:

Answer is A.

Suppose the pickpocket is caught at a time t after motorcycle starts. The distance traveled by the motorcycle during this interval is
$s\, =\, \displaystyle \frac{1}{2}at^2$ ...(1)
During this interval the jeep travels a distance
s + d = vt ...(2)
By (1) and (2),
$\displaystyle \frac{1}{2}at^2\, +\, d\, =\, vt$
or,
$t\, =\, \displaystyle \frac{v \pm \sqrt{v^2\, -\, 2ad}}{a}$
The pickpocket will be caught if t is real and positive.
This will be possible if
$v^2\geq\, 2ad\, \quad\, or,\, \quad\, v \geq\, \sqrt{2ad}$
Hence, the pick pocket will be caught if $v^2\geq\, 2ad\, \quad\, or,\, \quad\, v \geq\, \sqrt{2ad}$.

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