IIT JEE , AIEEE Forum - Physics , Mechanics - How does a person know that he is in Non Inertial Frame?

Earth_saver

A person is locked up in a cabin with no windows. the cabin is rotating about its axis with an angular velocity

.A block relatively at rest is kept beside him. How will he define the equillibrium of the block?

rooney

Pendulum method. Hang a pendulum inside. The bob will experience an outward force due to rotation of cabin (centrifugal). Thus, it will make some angle with the vertical or be inclined.

tushar.vaidya

remember one thing that newtons second law(F=m*a) is valid in only inertial frame of refrence.In your problem it is assumed as earth.&the cabin will be noninertial.so there is one force due to accleration of the cabin(pseudo force).in showing equillibrium that pseudo force should also be taken.
in fbd of block take one unknown force.&sole it(for unknown force) in orer that all forces will follow newons second law.
so by calculating pseudo force he can identify that e is in the non inertial frame of refrence.

bhupesh

Dear
First thing why the block will be at equilibrium. ? Secondly If you are thinking of Challenging Einstein then I would say its true only on inertial frame of reference.Though you can certainly say that you are on a non inertial frame reference. ( If you can stand still on the friction less floor of the cabin ( I am assuming that you want to define equilibrium with out any horizontal force ))

tarun_bits

dont go to the equivalence principle

Earth_saver

@Mr. Bhupesh, I didnt understand how i am challenging Einstein ? what if friction is present? I wanted to ask if the person inside will know he is in non inertial frame or a person outside will know it?

@tarun_bits, why cant i apply equivalence concept?

Conjurer

He will know because he will experience force in some other direction other than the vertically downward force due to gravity. Pseudo force and gravity will be the net force on him which will tend to pull him at an angle.

chemicaltester

the person inside the room will experience a centrifugal force
i.e the person will be tented to thrown outwards

computer001

i dont think he person will realize abt non-intertial frame...jus lik v on earth do not realize v r on a non-inertial frame tho earth itself is accelerating

computer001

The person outside will realize though

tarun_bits

let me tell you some interesting things about this>>>

1) Suppose you are in a closed lift and it is in free fall...

......you WILL be weightless ...wether you are falling in space or you are falling near earth,,,,,can you distinguish between the situations,,

can you tell wether you are in space or near earth.....you cant`.....your pendulum wont` work here...

2) Again you are in the lift and it is kept on the earths surface...the normal reaction will tell you your weight...

...now suppose it is accelerating in upwards with a magnitude of g....now whrn u are sitting in it and observing inside the lift..you feel a pseudo force downwards...which causes a normal reaction which says ur weight.....can u again between the two....

here you will see the equality of gravitational and inertial mass....

Earth_saver

Tell me if its correct- The prson inside will feel d pseudo force on him. Thus he will b able to identify pseudo frce on block as well?

claracishazephyr

Its a simple concept...any object in non-inertial reference frame [that is.where v cannot apply newton's laws of motin]....will experience an additional force apart from the oder such as wieght an all.....it will experience the pseudo force...and that pseudo force will account fr an equillibrium condition.The person as such will nt b able to feel the pseudo force coz hes in equillibrium...he's standing isint it?...he isint tilting or falling..it'll only b wen the magnitude of force varies..that the equillibrium b disturbed and thus then v cn gather if he experiencec any kind of force or nt...same fr the block..thats abt it

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