Slides in this set
· The frictional force between two surfaces is given by:
- when there is no sliding except in limiting equilibrium*
- in limiting equilibrium
- when sliding occurs
· The frictional force always acts in the direction opposite to sliding
· The value of the normal reaction is affected by a force which has a
component perpendicular to the direction of sliding.…read more
Moments of forces
· Moment about 0 = Fd, where d is the perpendicular distance
from O to the line of action of F.
· The unit for a moment is the Nm
· Anticlockwise=positive, clockwise=negative
· If in equilibrium:
clockwise moments = anticlockwise moments
· When three non-parallel forces are in equilibrium, their lines
of action are concurrent…read more
Centre of mass
· Weight acts through the centre of mass.
· The centre of mass of a body has the property that:
the moment, about any point, of the whole mass of the body taken at the
centre of mass is equal to the sum of the moments of the various particles
comprising the body.
· In one dimension:
· In two dimensions:…read more
Energy, work and power
· Work done = Fs , where s is the distance moved in the direction of the
· KE= ½ mv2 = energy due to a body's motion.
· Work-energy principle: the total work done by all the forces acting on a
body is equal to the increase in the kinetic energy of the body.
· GPE = mgh. It is the work done against g in raising the body.
· Mechanical energy (KE and PE) is conserved when no forces other than
gravity do work.
Initial (PE + KE) = final (PE + KE)
· Power is the rate of doing work, P=Fv.…read more