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ModPhy1/Unit1/Special Relativity/Inertial Frame/Law of Inertia/ |
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Isolated Object |
An Isolated Object is an object completely free of all external forces. Since there are only four forces known to exist in nature (gravity, electromagnetism, strong nuclear, and weak nuclear), an object can be isolated simply by eliminating all four of these forces.
Since all of the forces on an isolated object are zero, the total, net, or resultant force on an isolated object is also zero. Such an object is said to be in equilibrium.
Another way to obtain equilibrium is to balance one force against another
such that the vector sum of all the forces acting on the object equals zero.
For example, you could use an upward normal force (electromagnetic) to oppose the
downward weight (gravitational) of an object, and a forward string tension
(electromagnetic) to balance the backward surface friction (electromagnetic).
Although such an object would not be isolated in the strictest sense (external
forces would still be acting on the object), its motion would be the same as an
isolated object because the net force in both cases would be the same (namely
zero). Since the net force on an object determines its motion, the motion of an
object in equilibrium is indistinguishable from that of an isolated object.
Q1. Eliminating Nuclear Forces.
Which of the following methods would be most practical for isolating an object
from external nuclear forces (whether it be the strong nuclear force or the
weak nuclear force)? (A) Place the object more than one
atomic diameter from the source of the nuclear force. (B)
Make the object out of material insensitive to nuclear forces. (C) Introduce additional opposing nuclear fields to cancel out
the effect of the original nuclear field. (D) Introduce
additional opposing electromagnetic fields to cancel out the effect of the
original nuclear field. (E) Introduce an additional
opposing gravitational field to cancel out the effect of the original nuclear
field.
Q2. Eliminating Electromagnetic Forces.
Which of the following methods would be most practical for isolating an object
from an external electromagnetic force. (A) Place the
object more than a few atomic diameters from the source of the electromagnetic
force. (B) Make the object out of material insensitive
to electromagnetic force. (C) Introduce additional
opposing nuclear fields to cancel out the effect of the original
electromagnetic field. (D) Introduce additional
opposing electromagnetic fields to cancel out the effect of the original
electromagnetic field. (E) Introduce an additional
opposing gravitational field to cancel out the effect of the original
electromagnetic field.
Q3. Eliminating Gravitational Forces.
Which of the following methods would be most practical for isolating an object
from an external gravitational force. (A) Make the object
out of material insensitive to gravitational forces. (B)
Introduce additional opposing nuclear fields to cancel out the effect of the
original gravitational field. (C) Introduce additional
opposing electromagnetic fields to cancel out the effect of the original
gravitational field. (D) Introduce an additional
opposing gravitational field to cancel out the effect of the original
gravitational field. (E) Simply ignore the
gravitational force, treating it as an inertial or fictitious force.
Q4. An object can be isolated from
which of the following forces by placing it more than a few atomic diameters
away from the source of the force? (A) Gravitational Force (B) Electromagnetic
Force (C) Both Strong and Weak Nuclear Forces (D) More than one of these. (E)
None of these.
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ModPhy1/Unit1/Special Relativity/Inertial Frame/Law of Inertia/