MECHANICS
MOMENTS
Moment: turning affect of a force around a turning point.
• M=Exd← Perpendicular distance between line of action of
Moment, Nm Force, N force and turning point, m
Principal of moments: for a body to be in equilibrium the sum of the clockwise moments about any point equals the
sum of the anti-clockwise moments about the same point.
COUPLES
Couple: a pair of forces of equal size which act parallel to each other but in opposite directions. A couple doesn’t cause a
resultant linear force but does produce a turning effect.
• M=Exd← Perpendicular distance between lines of action of
Moment, Nm Force, N the forces, m
CENTRE OF MASS FORCES ON SUPPORTS
1mg 1mg Lmg The force on each support depends on the position in relation to the
No resultant Net anti- Net clockwise objects centre of mass. Anti-clockwise and clockwise moments must be
moment. clockwise moment. Bus equal so the support closer to the centre of mass will experience a
Bus is stable. moment. will topple. larger force.
But will right
itself.
UNIFORM ACCELERATION
Displacement: how far an object has travelled from its starting point in a given direction. (Vector.)
Velocity: the rate of change of an objects displacement ie it’s speed in a given direction. (Vector.)
Acceleration: the rate of change of an objects velocity. (Vector.)
✓ = utat DRAG
Air resistance causes a drag for e that acts in the opposite direction to motion and
affects the trajectory of a projectile. The horizontal component of drag reduces the
S =
tx¥ horizontal speed of the projectile and the horizontal distance it will travel. If the
'
S =
utttzat projectile has a verticale component of velocity, drag reduces the maximum
' height the projectile will reach and steepens the angle of decent.
s =vt -
fat
✓2= U2T 2AS
MOMENTS
Moment: turning affect of a force around a turning point.
• M=Exd← Perpendicular distance between line of action of
Moment, Nm Force, N force and turning point, m
Principal of moments: for a body to be in equilibrium the sum of the clockwise moments about any point equals the
sum of the anti-clockwise moments about the same point.
COUPLES
Couple: a pair of forces of equal size which act parallel to each other but in opposite directions. A couple doesn’t cause a
resultant linear force but does produce a turning effect.
• M=Exd← Perpendicular distance between lines of action of
Moment, Nm Force, N the forces, m
CENTRE OF MASS FORCES ON SUPPORTS
1mg 1mg Lmg The force on each support depends on the position in relation to the
No resultant Net anti- Net clockwise objects centre of mass. Anti-clockwise and clockwise moments must be
moment. clockwise moment. Bus equal so the support closer to the centre of mass will experience a
Bus is stable. moment. will topple. larger force.
But will right
itself.
UNIFORM ACCELERATION
Displacement: how far an object has travelled from its starting point in a given direction. (Vector.)
Velocity: the rate of change of an objects displacement ie it’s speed in a given direction. (Vector.)
Acceleration: the rate of change of an objects velocity. (Vector.)
✓ = utat DRAG
Air resistance causes a drag for e that acts in the opposite direction to motion and
affects the trajectory of a projectile. The horizontal component of drag reduces the
S =
tx¥ horizontal speed of the projectile and the horizontal distance it will travel. If the
'
S =
utttzat projectile has a verticale component of velocity, drag reduces the maximum
' height the projectile will reach and steepens the angle of decent.
s =vt -
fat
✓2= U2T 2AS
