A bird is singing on a tree and a man is hearing at a distance "r" from the bird. Calculate the displacement of the man towards the bird so that the loudness heard by man increases by "20dB" .[Assume that the motion of man is along the line joining the bird and the man :-

A bird flies for 4s with a velocity V=(t-2) m//s in a straight line where t= time in second Calculate the displacement and distance covered by the bird

A man goes 10 m towards North, then 20 m towards east then displacement is

A man is standing at a distance of 12 m from a cliff. Will he be able to hear a clear echo of his sound? Give a reason for your answer.

A man stands on the ground at a fixed distance from a siren which emits sound of fixed amplitude. The man hears the sound to be louder on a clear night than on a clear day.

A train, travelling at 20 km//hr is approaching a platform. A bird is sitting on a pole on the platform. When the train is at a distance of 2 km from pole, breakes are applied which produce auniform deceleration in it. At that instant the bird flies towards the train at 60 km//hr and after touching the nearest point on the train flies back to the pole and then flies towards the train and continues repeating itself. Calculate how much distance will the bird have flown before the train stops?

A man weighing 70 kg is standing at the centre of a flat boat of mass 350 kg. The man who is at a distance of 10 m from the shore walks 2 m towards it and stops. How far will he be from the shore? Assume the boat to be of uniform thickness and neglect friction between boat and water?

A string of negligible thicknes is wrapped several times around a cylinder kept on a rough horizontal surface. A man standing at a distance l from the cylinder holds one end of the sitting an pulls the cylinder towards him figure. There is no slipping anywhere. The length of the string passed through the hand of the man whicle the cylinder reaches his hands is

A man standing 48 m away from a wall fires a gun. Calculate the time after which an echo is heard. (The speed of sound in air is 320 m s^(-1) ).

A flag leaning to wards the east is inclined at an angle theta to the ground. A man walks a distance of 4 m from the foot of the flag towards the west and the observes the angle of elevation of the top of the flag to be 45^(@) . If, on walking a further distance of 3 m in the same direction, the angle of elevation decreases by 15^(@), tan theta is equal to

Secretion of aldosterone in birds, man, and other mammals is stimulated by