PHYSICS DEFINITION:
Principle of moments: Sum of clockwise moments about
a point is equal to the sum of the anticlockwise moments about the same point
provided the body is in equilibrium.
PHYSICS KEYWORD LIST:
Resultant Force: Single force that has the same
effect as all of the forces acting on an object.
Triangle of forces: Closed triangle drawn for an
object in equilibrium. The sides of the triangle represent the forces in both
magnitude and direction.
Equilibrium: Object in equilibrium is either at rest
or travelling with a constant velocity because the resultant force on it is
zero.
Components (of a vector): Magnitudes of a vector
quantity in 2 perpendicular directions.
Resolving (the vector): Splitting a vector (such as
force) into 2 vectors at right angles.
Free-body force diagram: Diagram showing all the
forces acting on an object (but not the forces it exerts on other objects).
Centre of gravity: Point where the entire weight of
an object appears to act.
Moment of a force: Moment of a force about a point is
the product of the force and perpendicular distance from the line of action of
the force to the point.
Couple: Pair of equal and opposite forces that act on
an object at different points and produce rotation only.
Torque (of a couple): Product of one of the forces
and the perpendicular distance between the forces.
PHYSICS CHAPTER WISE SUMMARY:
Forces are vector quantities that can be added using a
vector triangle. Their resultant can be determined using trigonometry or by
scale drawing.
Forces can be resolved into components. Components at right
angles to one another can be treated independently of one another. The
components are:
x-direction: F Cos angle
y-direction: F Sin angle
The moment of force = force x perpendicular distance of the
pivot from the line of action of the force.
The principle of moments states that, for any object in
equilibrium, the sum of clockwise moments about any point provided by the
forces acting on the object is equal to the sum of anticlockwise moments about
that same point.
A couple is a pair of equal, parallel but opposite forces
whose effect is to produce a turning effect on a body without giving it linear
acceleration.
Torque of a couple = one of the forces x perpendicular
distance between the forces.
For an object in equilibrium, the resultant force acting on
the object must be zero and the resultant moments must be zero.
PHYSICS IMPORTANT NOTES:
The moment of force = force x perpendicular distance of the
pivot from the line of action of the force.
Torque of a couple = one of the forces x perpendicular
distance between the forces.
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