The tangential force acting on an object that opposes it from sliding freely on the adjacent surface is called

Two tuning forks of frequencies 6Hz and 4Hz respectively are sounded together. The beat frequency is 

The capacitance of a capacitor, C, is inversely proportional to

The value of R in the above circuit to make the galvanometer measure 2A is 

An object is placed 25cm in front of a convex mirror has its image formed 5cm behind the mirror. what is the focal length of the convex mirror