1.1 what is work done?when a force acts on a body it gets dsplased in any direction exept in the direction
perpendicular to the work done.FORMULA(w=f.s)
when the displacement is produced in the direction applied force angle=0,w=fs
work is a scalar product as it is a dot product
1.2 when is work said to be 1j?when a work of 1N displaces a body through 1m in its direction.1joule=(10)-1ergs
1.3 when is work is said to be positive?work is said to be +ve when the
angle is acute and cosine angle is <90.EG:-when a loaded spring is
strecthed the work done by stretching force is positive.
a freely falling body posses a angle of 0degree.
1.4 when is work is said to be negative?work is said to be negative when the angle is obtuse and cosine angle lie between 90and180 degree EG:-when a body is moved in a rough surface work done by the frictional force is negative.
1.5 when is work said to be zero?when a force is applied and if displacement is 0 then work done will be 0 EG:-WHEN A
person carrying a load on his head and moving horizontaly. the angle between f and s is 90 then the work done is 0.
1.6 what do you mean by conservative and non conservative forces?conservative force means if
the work done by or against the force in moving a body depen depends only on the intial and
final position of the body and not by the path followed.non conservative forces means if the
work done by or against the force in moving the body depends on the path followed between
the intial and final point.
eg of conservative forces are elastic spring ,magnetic force ,electrostatic force.
eg of non conservative forces are frictional forces ,viscus force ,induction forces.
2 key concepts(energy)
2.1 wht is power and energy?power means
rate at which a body can do work. while a
energy means a ability to do a work
mechanical energy is classified int two types they are k.e and p.e
2.2 what is a kinetic energy?energy possed by a body by the virtue of
motion eg:-water mill works with water flow
2.3 wht do you mean by the potential energy of elastic spring?the
potential energy of a spring according to state of compression or
stretching.when a spring is stretched