question_answer

A body of weight 30 N falls freely from a height of 15 m and buries into sand through a distance of 0.5 m. Find the resistance due to sand.

Answer:

As the body reaches B the K.E. = P.E. at A. As it moves to C there is also a loss in P.E. which is equal to\[mg{{h}_{1}}.\] The total loss of \[P.E.=mgh+mg{{h}_{1}}=\] \[(30\times 15\times 30\times 0.5)\] Work done\[=mg(h+{{h}_{1}})\] \[F\times 0.5=30\times 15.5\Rightarrow F=30\times 31=930N.\]