A) 20 J
B) 30 J
C) 40 J
D) 10 J
Correct Answer: A
Solution :
Key Idea The energy lost due to air friction is equal to difference of initial kinetic energy and final potential energy. |
Initially body posses only kinetic energy and after attaining a height the kinetic energy is zero. |
Therefore, loss of energy \[=KE-PE\] |
\[=\frac{1}{2}\,m{{v}^{2}}-\,mgh\] |
\[=\frac{1}{2}\,\times 1\times 400-1\times 18\times 10\] |
\[=200-180=20\,J\] |
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