Mechanics and Materials

Mechanics and Materials


Moments
☆ The moment of a force about a point is the product of the force
and the distance from its line of action to the point.
Moment (Nm) = Force (N) x Perpendicular Distance (m)

☆ Where an object is in equilibrium, the moments on it about a
point are balanced.
Total Clockwise Moment = Total Anticlockwise Moment

☆ A couple is a pair of equal and opposite parallel forces acting
on the same body that do not act in the same line.
Moment of a Couple (Nm) = Force (N) x Perpendicular Distance
Between Lines of Action (m)


Centre of Mass
☆ The centre of mass is where the mass of an object can be
considered to be concentrated.
☆ The line of action acts from the centre of mass and shows how
gravity is acting upon the object.

☆ The centre of mass can be found by suspending an object by a pin
and then using a plum line to draw on the line of action where
they cross is the centre of mass.

☆ If the line of action falls outside of the width of the base then
the object will topple.


Newton’s Laws of Motion
☆ Newton’s First Law:
☆ ‘An object in constant motion or at rest will remain in
constant motion or at rest unless acted on by a resultant
force’.
☆ Newton’s Second Law:
☆ F = ma (force in N equals mass in kg times the acceleration
in ms-2).
☆ Newton’s Third Law:
☆ ‘Every force has an equal and opposite force’.


SUVAT and Projectiles
☆ S= Displacement
☆ U= Initial velocity
☆ V= Final velocity
☆ A= Acceleration
☆ T=Time