A force of 15 N is required to pull up a body of mass 2 kg through a distance 5 m along an inclined plane making an angle of 30^(@) with horizontal as shown in fig calculate : (i)the work done by the force in pulling the body. (ii)The force due to gravity on the body, (iii)the work done against by the force due to gravity Take :g=9.8 m s^(-2). (iv)Account for the difference in answers of part (i) and part (iii).

A force of 15 N is required to pull up a body of mass 2 kg through a d

1.	A force of 15 N is required to pull up a body of mass 2 kg through a distance 5 m along an inclined plane making an angle of 30^(@) with horizontal as shown in fig calculate : (i)the work done by the force in pulling the body. (ii)The force due to gravity on the body, (iii)the work done against by the force due to gravity Take :g=9.8 m s^(-2). (iv)Account for the difference in answers of part (i) and part (iii).
Answer» Solution : (i)Work done by the FORCE in pulling the body up W=Force x displacement in the direction of force =15 N `xx`5 m=75 J (ii)Force DUE to gravity on the body `F=mg=2xx9.8=19-6N` (iii)Work done against the force due to gravity W.=Force due to gravity `xx` vertical height moved But in right ANGLED `DELTAACB` sin `30^(@)=(BC)/(AB)` `therefore BC=AB sin 30^(@)` Hence W.=mg `xx` AB sin `30(@)` `=19.6xx5xx(1)/(2) (because sin 30^(@)(1)/(2))` (iv)We note that W `gt` W. .The difference in work W and W. is 75 J-49 J =26 J.ACtually 26 J is the work done against the force of friction between the body and the inclined plane .