A heavy box of mass $$50 \mathrm{~kg}$$ is moving on a horizontal surface. If co-efficient of kinetic friction between the box and horizontal surface is 0.3 then force of kinetic friction is :

A man carrying a monkey on his shoulder does cycling smoothly on a circular track of radius $$9 \mathrm{~m}$$ and completes 120 resolutions in 3 minutes. The magnitude of centripetal acceleration of monkey is (in $$\mathrm{m} / \mathrm{s}^2$$ ) :

A series LCR circuit is subjected to an ac signal of $$200 \mathrm{~V}, 50 \mathrm{~Hz}$$. If the voltage across the inductor $$(\mathrm{L}=10 \mathrm{~mH})$$ is $$31.4 \mathrm{~V}$$, then the current in this circuit is _______.

Which of the following statement is not true about stopping potential $$(\mathrm{V}_0)$$ ?