Work Energy And Power Question 70
Question: An open knife edge of mass ’m’ is dropped from a height ‘h’ on a wooden floor. If the blade penetrates upto the depth ’d’ into the wood, the average resistance offered by the wood to the knife edge is [BHU 2002]
Options:
A) $ mg $
B) $ mg( 1-\frac{h}{d} ) $
C) $ mg( 1+\frac{h}{d} ) $
D) $ mg{{( 1+\frac{h}{d} )}^{2}} $
Show Answer
Answer:
Correct Answer: C
Solution:
Let the blade stops at depth d into the wood. $ v^{2}=u^{2}+2aS $
therefore $ 0={{(\sqrt{2gh})}^{2}}+2(g-a)d $ by solving $ a=( 1+\frac{h}{d} )g $ So the resistance offered by the wood $ =mg( 1+\frac{h}{d} ) $
