A n space o b j e c t space o f space m a s s space m space i s space t i e d space t o space a space s t r i n g space o f space l e n g t h space l space a n d space a space v a r i a b l e space f o r c e space F space i s space a p p l i e d space o n space i t space w h i c h space b r i n g s space t h e space s t r i n g space g r a d u a l l y space a t space a n g l e space theta space w i t h space t h e space v e r t i c a l. space F i n d space t h e space w o r k space d o n e space b y space t h e space f o r c e space F. space

Asked by medha painuly | 14th Oct, 2014, 12:22: PM

Expert Answer:

Let m be the mass of an object tied to a string of length l. A variable force F is applied to bob.
Let θ be the angle with vertical as shwon in figure.
 
Accroding to work - Energy theorem,
Change in P.E.=Work done
At pont A P.E. is zero , when it comes at pont B P.E. is maximum 
ΔU=mgL-mgLcosθ=mgL(1-Lcosθ)
hence work done W=mgL(1-Lcosθ)
 
 

Answered by Priyanka Kumbhar | 16th Oct, 2014, 09:28: AM

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