(a) A force has zero moment about any point along its line of action. (b) A force has no moment about a line parallel to its line of action. (c) The magnitude of the moment of a force about a line equals the product of the component of the force perpendicular to the line and the distance between this component and the line.

Elements Of Electromagnetics
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Author:Sadiku, Matthew N. O.
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Answer true or false in response to the following questions:
(a) A force has zero moment about any point along its line of action.
(b) A force has no moment about a line parallel to its line of action.
(c) The magnitude of the moment of a force about a line equals the product of the
component of the force perpendicular to the line and the distance between this
component and the line.
(d) The moment about a point P of the sum of a set of concurrent forces, placed at
the point of concurrency (point P), equals the sum of the moments about P of
the separate forces.
(e) A couple has the same moment about any point.
(f) If we know the moment of a couple about a point A, then we can find the moment
of the couple about a specified line BC even if A does not lie on BC.
(g) Two force and couple systems are equipollent if they have either the same resul-
tant force or if the moments about some point P are the same for both systems.
(h) It is possible for a system consisting of a single couple to be equipollent to a
system of one force and 99 couples.
(i) Given any system of forces and couples, and any point P, the system may be
reduced to an equipollent system comprising of a force at P and a couple (where
either or both might be zero).
(j) If a system S₁ of forces and couples has a "force-alone" (single force resultant)
equipollent system S2, then S₁ must be a coplanar force system.
(k) The simplest resultant of a general system of forces and couples is a "wrench"
or "screwdriver," that is, a collinear force and a couple along a specific axis in
space.
(1) Let a general system of forces and couples be resolved into a resultant force at
P and an accompanying couple. If the couple is normal to the force, then the
equipollent wrench consists of a single force.
(m) If a body is in equilibrium under the action of three forces, and two of these
intersect at a point P, then the line of action of the third also passes through P.
(n) If a body equilibrium und four forces, two of which for a couple, then
the other two also form a couple.
(o) If a body is in equilibrium under the action of three forces, the forces need not
be coplanar.
(p) It is possible for a body acted on by a single couple to be in mechanical equilib-
rium.
(q) If the external forces acting on a body satisfy ΣF = 0 and ΣMk = 0; then the
body must be at rest.
(r) The tensions in a cable passing over a pulley in equilibrium are always equal.
(s) It is possible for a body to be in equilibrium with two separate parts comprising
the body not being in equilibrium separately.
(t) The action-reaction principle (Newton's 3rd law) plays no role when constructing
free-body diagrams of various parts of a rigid structure subjected to external
forces.
Transcribed Image Text:Answer true or false in response to the following questions: (a) A force has zero moment about any point along its line of action. (b) A force has no moment about a line parallel to its line of action. (c) The magnitude of the moment of a force about a line equals the product of the component of the force perpendicular to the line and the distance between this component and the line. (d) The moment about a point P of the sum of a set of concurrent forces, placed at the point of concurrency (point P), equals the sum of the moments about P of the separate forces. (e) A couple has the same moment about any point. (f) If we know the moment of a couple about a point A, then we can find the moment of the couple about a specified line BC even if A does not lie on BC. (g) Two force and couple systems are equipollent if they have either the same resul- tant force or if the moments about some point P are the same for both systems. (h) It is possible for a system consisting of a single couple to be equipollent to a system of one force and 99 couples. (i) Given any system of forces and couples, and any point P, the system may be reduced to an equipollent system comprising of a force at P and a couple (where either or both might be zero). (j) If a system S₁ of forces and couples has a "force-alone" (single force resultant) equipollent system S2, then S₁ must be a coplanar force system. (k) The simplest resultant of a general system of forces and couples is a "wrench" or "screwdriver," that is, a collinear force and a couple along a specific axis in space. (1) Let a general system of forces and couples be resolved into a resultant force at P and an accompanying couple. If the couple is normal to the force, then the equipollent wrench consists of a single force. (m) If a body is in equilibrium under the action of three forces, and two of these intersect at a point P, then the line of action of the third also passes through P. (n) If a body equilibrium und four forces, two of which for a couple, then the other two also form a couple. (o) If a body is in equilibrium under the action of three forces, the forces need not be coplanar. (p) It is possible for a body acted on by a single couple to be in mechanical equilib- rium. (q) If the external forces acting on a body satisfy ΣF = 0 and ΣMk = 0; then the body must be at rest. (r) The tensions in a cable passing over a pulley in equilibrium are always equal. (s) It is possible for a body to be in equilibrium with two separate parts comprising the body not being in equilibrium separately. (t) The action-reaction principle (Newton's 3rd law) plays no role when constructing free-body diagrams of various parts of a rigid structure subjected to external forces.
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