Tag: concept of inertia

Questions Related to concept of inertia

A water tanker filled up to $\dfrac {2}{3}$rd of its height is moving with a uniform speed. On sudden application of the brake, the water in the tank would

  1. move backward

  2. move forward

  3. be unaffected

  4. rise upwards


Correct Option: B
Explanation:

Basically, the law of motion is that an object at rest stays at rest and an object continues in motion until an external force acts on it.
Inertia is the resistance of any physical object to any change in its state of motion, including changes to its speed and direction. It is the tendency of objects to keep moving in a straight line at constant velocity.


So, on sudden application of brakes on the water tank, the water tank decelerates or may even stop but the water in the tank still has a tendency to move forward due to inertia. Hence the water in the tank would move forward.
A water tanker filled up to two-thirds of its height moving with a uniform speed, on sudden application of the brake, the water in the tank would move forward.

If a train is retarding and at same time coin is thrown upwards, then you will observe that:

  1. the coin reaches again in your hand

  2. the coin falls behind you

  3. the coin falls in front of you

  4. the coin follows a circular path


Correct Option: C
Explanation:

At t$=$0
Velocity of train$=$v
Velocity of coin$=$v(horizontal velocity in the direction of velocity of train)
at t$=$t
Velocity of train$=$v-$\Delta$ v
Velocity of coin$=$v
Distance travelled by train after retarding$=$(v-$\Delta$v)t
Distance travelled by coin$=$v$\times$t   which is greater than distance travelled by train.
So,the coin will fall infront of you.


A football has lesser inertia than a stone of the same size because:

  1. Football has more air inside than the stone.

  2. Football has less air inside than the stone.

  3. Football has less mass than the stone.

  4. Football has more mass than the stone.


Correct Option: C
Explanation:

Inertia is the property of mass. Mass of stone $>$ mass of football.

When a tree with a flexible stem is shaken vigorously,its fruits and leaves fall  own.This phenomenon can be explained by making use of

  1. Newton's first law of motion

  2. Newton's second law of motion

  3. Newton's third law of motion

  4. Law of conservation of momentum


Correct Option: A
Explanation:

 

There are three types of inertia:
1. Inertia of rest: This is the resistance offered by the body to remain in rest unless an external force is not applied on the body. Eg. : If a carpet is beaten with a stick then the dust particles due to inertia of rest tends to remain in rest while the fibres of carpet becomes in motion.


2. Inertia of direction: This is the resistance offered by the body to change its direction unless an ext. force is not applied on the body. Eg : If a bus takes a turn then passengers sitting in tends to remain in the same direction in which the bus was travelling before.


3. Inertia of motion: The resistance offered by the body to change its uniform motion. Eg : If a bus stops suddenly then the passengers fall forward due to inertia of motion

So when we shake a tree, due to inertia of motion the fruit tries to remain in motion. Due to which it gets detached from the branch and falls.

A and B are two objects with mass 6 kg and 34 kg respectively. Then

  1. A has more inertia than B

  2. B has more inertia than A

  3. A and B both have same inertia

  4. none of the above is true


Correct Option: B
Explanation:

Inertia has direct dependence on $mass$. More is the mass of the body, more is the inertia.

Since, B has more mass, thus B has more inertia than A. 

P and Q are two objects with masses 5 kg and 30 kg respectively. Then

  1. P has more inertia than Q

  2. Q has move inertia than P

  3. P and Q have the same inertia

  4. neither P nor Q has any inertia


Correct Option: B
Explanation:

Inertia has direct dependence on $mass$ of the body. More the mass of the body, more will be its inertia.

Since Q has more mass, thus Q has more inertia than P.

Why can dust be removed from a carpet by shaking it, or by beating it with a stick?

  1. Because of inertia of rest

  2. Because of inertia of motion

  3. Because of inertia of direction

  4. Because of momentum


Correct Option: A
Explanation:

When the carpet is shaken or beaten by a stick, then the carpet moves back but the dust remains still due to inertia of rest and hence the dust particles get separated out.

Which will have move inertia?

  1. A plastic eraser

  2. Pencil

  3. A book

  4. A table


Correct Option: D
Explanation:

The object having the greatest mass has the greatest inertia.

As the the table is the heaviest object among the given options, thus table will have more inertia.

Why athletes stop themselves before the line marked for javelin throw

  1. Due to inertia of rest

  2. Due to inertia of motion

  3. Due to inertia of direction

  4. All


Correct Option: B
Explanation:

Due to inertia of motion, an object do not stop all of a sudden rather it continues to move over some distance. Hence the athletes stop themselves much before line marked so that they come to rest before crossing that line, otherwise it is said to be a foul.

The sparks produced during sharpening of a knife against a grinding wheel leaves the rim of the wheel tangentially. This is due to which of the following?

  1. Inertia of rest

  2. Inertia of motion

  3. Inertia of direction

  4. Force applied


Correct Option: C
Explanation:

Just after the sparks are produced, the force acting on the sparks becomes zero and due to inertia of direction, they start to move in their initial direction of motion which is tangential to the rim of the grinding wheel.