\(W=\vec{F}.(\vec{r_{f}}-\vec{r_{i}})\)
\(=(5\widehat{i}+2\widehat{j}+7\widehat{k}).((5\widehat{i}-2\widehat{j}+\widehat{k})-(2\widehat{i}+2\widehat{j}-4\widehat{k}))\)
\(W=40J\)
So, The correct answer is 40.
A block of certain mass is placed on a rough floor. The coefficients of static and kinetic friction between the block and the floor are 0.4 and 0.25 respectively. A constant horizontal force \( F = 20 \, \text{N} \) acts on it so that the velocity of the block varies with time according to the following graph. The mass of the block is nearly (Take \( g = 10 \, \text{m/s}^2 \)): 
0.01 mole of an organic compound (X) containing 10% hydrogen, on complete combustion, produced 0.9 g H₂O. Molar mass of (X) is ___________g mol\(^{-1}\).
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