chapter 5 turning effects of forces Flashcards
what is the turning effect of a force called
a moment
what can be used to show the concept of moment
a simple lever
what is a lever
a rigid bar resting on a pivot of fulcrum
what is the use of a lever
to move a load when a force is applied
the turning effect of the force is proportional to
-the perpendicular distance from the pivot where the force is applied
-the magnitude of the force applied
what is the turning effect of the force also known as
a torque
si unit of moment of a force
newton meter (N m)
is newton meter a scalar or vector quantity
vector quantity
a clockwise rotation about a pivot is
a clockwise moment
an anticlockwise elation about the pivot is an
anticlockwise moment
M=
Fd
(moment of force= force applied x perpendicular dist. from pivot to line of action of force)
state the principle of moments
the principle of moments states that when a body is in equilibrium, the sum of clockwise moments about a pivot is equal to the sum if anticlockwise moments about the same point
when a lever is balanced we can say that
it is in equilibrium
for an object to be stationary or in equilibrium,
it must not have any rotational or translational motion
(there should be no resultant moments and no resultant force acting on the body)
conditions for a body to be in equilibrium
- the resultant moment on the body is zero
- the resultant force on the body is also zero
center of gravity
the centre of gravity of an object is an imaginary point where the entire weight of the object seems to act
for a body to be balanced
the sum if clockwise moments due to the individual particles must be equal to the sum of anticlockwise moments
how do we find the centre of gravity of an irregularly shaped laminate
Cut out irregular lamina from cardboard.
Make 3 holes near the edge, spaced apart.
Suspend from one hole using a pin.
Hang a plumb line from the same pin.
Mark the line on the lamina.
Repeat for other holes.
Draw straight lines through marks—intersection is the center of gravity.
stability
the stability to an object is a measure of its ability to return to its original positiom
ways that stability of an object can be affected
the position of the centre of gravity
area of the base of the object
position of the centre of gravity
the lower the centre of gravity of an object, the more stable it is
area if the base of an object
the larger the base area of an object the more stable it is
