An electric fan, with effective area of cross-section 'A', accelerates air of density `rho` to a speed 'v'. What is the power needed for this process ?

A plank of area of cross-section A is half immersed in liquid 1 of density rho and half in liquid 2 of density 2rho . What is period of osciallation of the plank if it is slightly depressed downwards?

Statement- 1 : When an electric fan is switched on in a closed room, the air of the room is cooled. Statement- 2 : When fan is switched on, the speed of the air molecules will increase.

Cylindrical block of area of cross-section A and of material of density rho is placed in a liquid of density one third of density of block. The block compress in the spring is one-third of te length of the block. if acceleration due to gravity is g, the spring constant of the spring is

If a solid cylinder of area of cross-section A is moving with velocity V in medium of density p then power loss of cylinder is

A rectangular block of mass m and area of cross-section A floats in a liquid of density rho . If it is given a small vertical displacement from equilibrium, it undergoes oscillation with a time period T. Then

A block of rectangular size of mass m and area of cross section A, float in a liquid of density rho .If we give a small vertical displacement from equilibrium, It undergoes SHM with time period T, then

The flow speeds of air on the lower and upper surfaces of the wing ofan aeroplane are v and sqrt2v respectively. A is the area of the wing and rho is the density of th e surrounding air. What is the force of the dynamic lift on the wing ?

A conducting wire of length 'I', area of cross-section A and electric resistivity rho is connected between the terminals of a battery. A potential difference V is developed between its ends, causing an electric current. If the length of the wire of the same material is doubled and the area of cross-section is halved, the resultant current would be: