Introduction to motion - class-IX

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

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

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

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

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

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.

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.

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

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 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.

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

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