An open knife edge of mass 200g is dropped from height 5m on a cardboard. If the knife edge penetrates distance 2m into the cardboard, the average resistance offered by the cardboard to the knife edge is
Options
(a) 7N
(b) 25N
(c) 35N
(d) None of these
Correct Answer:
7N
Explanation:
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We can use work energy theorem ,
Total kinetic energy lost is K=mg(h+d)
Work done by the resistance force F is W=Fd
By equating , we get Force =
mg(h+d)/d = [{(200/1000)×(5+2)}/2] N = [0.2×7÷2] N = 7N (ans)