Answer:
Technically everything has somewhat of a magnetic field. I guess
Answer:
I'm not really sure but I think it's choice a
Under the influence of gravity, objects just move down to the earth.
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We can solve the problem by applying Newton's second law, which states that the resultant of the forces acting on an object is equal to the product between its mass and its acceleration:

We should consider two different directions: the direction perpendicular to the inclined plane and the direction parallel to it. Let's write the equations of the forces along the two directions, decomposing the weight of the object (mg):

(parallel direction) (1)

(perpendicular direction) (2)
where

is the angle of the inclined plane, N is the normal reaction of the plane,

is the frictional force, with

being the coefficient of friction.
From eq.(2), we find

and if we substitute into eq.(1), we can find the acceleration of the block:

from which
There are two interchangeable concepts that can be applied to this theory. The first one is the moment of Inertia and the second the perioricity. When the runners put their leg forward they reduce their moment of inertia allowing their center of mass to maintain the speed they carry and not waste energy. In this way when they swing, the leg begins to act as a kind of pendulum, and remember that the pendulum is directly proportional to the length, that is,

In this way, by bringing their legs closer they reduce the distance and make the period shorter.