Tag: motion and reference point

Questions Related to motion and reference point

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

physics along with motion different types of motion basics of motion motion and reference point

  1. Linear

  2. one dimensional

  3. two dimensional

  4. both A and B

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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?

physics along with motion different types of motion basics of motion motion and reference point

  1. Circular

  2. Rectilinear

  3. Periodic

  4. All of the above

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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

physics motion and types of motion different types of motion basics of motion motion and reference point

  1. Uniform

  2. Accelerated

  3. Retarded

  4. Along a circular track

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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 :

physics motion and types of motion different types of motion basics of motion motion and reference point

  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.

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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   

physics motion and types of motion different types of motion basics of motion motion and reference point

  1. $=v$

  2. $<v$

  3. $>v$

  4. $\geq v$

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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  

physics motion and types of motion different types of motion basics of motion motion and reference point

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

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

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

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

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