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The Physics of Carpet Cleaning!

Why when a hanging carpet is beaten with a stick, the dust particles start coming out of it?

Please explain to me, in a simple language.

Asked Osho Garg


This is due to the inertia of rest of the dust particles.

When the mat is beaten suddenly with a stick, the mat moves forward, but the dust tends to remain at the same position on account of the inertia of rest. When the mat/ carpet moves, the dust particles lose support and they fall down

Numerical from Laws of Motion

Two cars a and b are moving towards each other on horizontal surface.the car a has mass 60 kg and moves towards the right with speed 60 m/s.the car b has mass 1000 kg and move towards the left with a speed 20m/sec.the two car collide and get stuck to each other.with what velocity will they move after collision

Asked Vinayak

Visitors are invited to answer.

Numerical (MCQ) from Kinematics

A person standing on an escalator takes time t1 to reach the top of a tower when the escalator is moving.he takes time t2 to reach the top of the tower when the escalator is standing.how long will he take if he walks up a moving escalator?
a)t2-t1    b)t1+t2    c)t1t2/(t1-t2)  d)t1t2/(t1+t2)


Please post your answers as comments

Newton’s Third Law of Motion and some doubts

Newton’s Third Law of Motion states that

“Every action has equal and opposite reaction”

In other words,

“Whenever a body exerts a force on another body, the second body exerts an equal and opposite force on the first body”

 Osho Garg asks:

“if a person is sitting on a chair both the chair and person exert force against it so we called that ” there is always an equal and opposite reaction ” but for example a elephant of mass 584 kg sit on a chair, the chair will broke.  So what we called for this . Please explain.



When an elephant “sits” on a chair, it breaks because it cannot give the “equal reaction” and  it “yields” to it.

Therefore, here the force is doing “work”.

More discussions are welcome

Solutions to I E Irodov

Water content in our body helps to regulate temperature stable.

Does the presence of large amounts of water in the body help keep body temperature stable? exp

Water Drop


Asked  Deryn


The answer is yes.

Here, the high value of specific heat capacity of water helps.

Drinking water helps regulating the body temperature during winter (extreme cold) as well as during summer.

I remember, schools had made it mandatory for students to dring water after every period during a summer time when the atmospheric temperature was too high and students used to faint often. The water treatment was very effective and the no. of students fainting due to high surrounding temperature decreased significantly.

If we consider the earth system also. it can be seen that the climate is moderate near water bodies.

Further, it is the abundance of water on earth which makes it a planet suitable for the existence of life.

Numerical Problems from Kinematics

1.      A stone is thrown in a vertically upward direction with a velocity of 5 m s-1. If the acceleration of the stone during its motion is 10 m s–2 in the downward direction, what will be the height attained by the stone and how much time will it take to reach there?

2.      Using a horizontal force of 200 N, we intend to move a wooden cabinet across a floor at a constant velocity. What is the friction force that will be exerted on the cabinet?

3.      A stone is thrown vertically upward with an initial velocity of 40 m/s. Taking g = 10 m/s2, find the maximum height reached by the stone. What is the net displacement and the total distance covered by the stone?

4.      A ball thrown up vertically returns to the thrower after 6 s.
(a)     The velocity with which it was thrown up,
(b)     The maximum height it reaches, and
(c)     Its position after 4 s.

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