If a ping pong ball and a basketnall were both dropped at the same time from the roof of our school ,which would hit the ground with a greater force ? common sense tells us that the basketball ball would. the difference in forces would be caused by the different masses of the balls . newton stated this relationship in his second law ,the force of an object is equal to its mass times its acceleration . what are two other situations where newton's 2nd law may apply ?

Newton never said that, and there's really no such thing as the "force of an object".

Newton said that the rate of change of an object's momentum is equal to the net force ACTING ON the object.  These days, almost everybody says that the object's acceleration, multiplied by its mass, is equal to the net force ACTING ON it.  This statement is entirely equivalent to the other one.

Newton's 2nd law applies everywhere, to simply all objects.

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i think it because equal matrices have equal dimensions, only square matrices can be symmetric. for all indices and . every square diagonal matrix is symmetric, since all off-diagonal elements are zero. in linear algebra, a real symmetric matrix represents a self-adjoint operator over a real inner product space.