A reference frame attached to the earth - 
a) is an inertial frame because Newton's laws of motion are applicable in this frame
b) is an inertial frame by definition
c) cannot be an inertial frame because earth is revolving around sun
d) None
Please explain

Dear Student,

Earth rotates around its axis as also revolves around the sun. In both these motion, centripetal acceleration is present. Therefore, strictly speaking earth or any frame of reference fixed on earth cannot be taken as an inertial fame. However, as we are dealing with speeds  ≈ x 108 ms-1 (speed of light) and speed of earth is only about 3 x 104 m/s, therefore when small time intervals are involved effect of rotation and revolution of earth can be ignored. Furthermore, this speed of earth can be assumed to be constant. Hence earth or any other frame of reference set up on earth can be taken as an approximately inertial frame of reference.

On the contrary, a frame of reference which is accelerated or decelerated is a non-inertial frame. Ans is B.


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Even if Newton's laws are applicable here, it doesnt become a de facto inertial frame.

Any frame undergoing acceleration is non inertial. So due to continuous centripetal force on it due to revolution around sun, STRICTLY speaking earth is a non inertial frame.

But for practical purposes since the velocity of earth is
Thus very strictly speaking, answer is C. Practically and for school purposes, answer is B.

And yes, Harper Lee weaved MAGIC in that book :)
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