Forces, pressure and density
• Centre of gravity, the point at which the whole weight of the object appears to
act.
• Force acts due to mass so the concept of centre of gravity is due to the point
mass. For example all the objects are attracted towards the centre of the earth
so it means that the mass of earth is more concentrated at the centre.
• Moment of Force: the product of force applied and perpendicular distance from
line of action of force to the pivot.
• Here the object is suspended using the rope to the roof and it is in equilibrium.
So we can take any point A,B,C,D,E as the pivot. But remember we take the point
pivot where there is a known distance from the line of action of force.
• The SI unit is Nm.
• Case : the two forces are not given so how to find those two forces [F1 AND F2]
and distance between B and E is d2.
1. Eliminate one force by taking it point as pivot so we take the point B as
the pivot hence:
, 0=F2d2
why we have taken the left side as 0? As w have taken point B as pivot so the distance of
F1 to pivot is 0.
• Case 2: the metal is attached from the point to the wall to make the object in
equilibrium which is attached to the wall. While A is the pivot.
We are to find F so the moment around W is W*d1.
While the moment due to F is F*d.
Then the force F moment is to find by resolving the force:
Fysinx*d2 while Fx is 0 as the line is passing through the
Centre of gravity.
Fy is the component of the anticlockwise moment thats why we
Have find it.
• Centre of gravity, the point at which the whole weight of the object appears to
act.
• Force acts due to mass so the concept of centre of gravity is due to the point
mass. For example all the objects are attracted towards the centre of the earth
so it means that the mass of earth is more concentrated at the centre.
• Moment of Force: the product of force applied and perpendicular distance from
line of action of force to the pivot.
• Here the object is suspended using the rope to the roof and it is in equilibrium.
So we can take any point A,B,C,D,E as the pivot. But remember we take the point
pivot where there is a known distance from the line of action of force.
• The SI unit is Nm.
• Case : the two forces are not given so how to find those two forces [F1 AND F2]
and distance between B and E is d2.
1. Eliminate one force by taking it point as pivot so we take the point B as
the pivot hence:
, 0=F2d2
why we have taken the left side as 0? As w have taken point B as pivot so the distance of
F1 to pivot is 0.
• Case 2: the metal is attached from the point to the wall to make the object in
equilibrium which is attached to the wall. While A is the pivot.
We are to find F so the moment around W is W*d1.
While the moment due to F is F*d.
Then the force F moment is to find by resolving the force:
Fysinx*d2 while Fx is 0 as the line is passing through the
Centre of gravity.
Fy is the component of the anticlockwise moment thats why we
Have find it.
