The sun is less bright at morning and evening as compared to at noon although its distance from the observer is almost the same. Why ?

The largest and the shortest distance of the earth from the sun are r_(1) and r_(2) , its distance from the sun when it is at the perpendicular to the major axis of the orbit drawn from the sun

The principle of 'parallax' in section 2.3.1 is used in the determination of distances of very distant starts. The baseline AB is the line joining the Earth's two locations six months apart in its orbit around the Sun. That is, the baseline is about the diameter of the Earth's orbit = 3xx10^(11)m . However, even the nearest stars are so distant that with such a long baseline, they show parallax only of the order of 1" (second) of arc or so. A parsec is a conventent unit of length on the astronomical scale. It is the distance of an object that will show a parallax of 1" (second of arc) from opposite ends of a baseline equal to the distance from the Earth to the Sun. How much is a parsec in terms of metres ?

The angular width of the central maximum in a single slit diffraction pattern is 60^(@) . The width of the slit is 1 mu m The slit is illuminated by monochromatic plane waves. If another slit of same width is made near it. Young's fringes can be observed on a screen placed at a distance 50 cm from the slits. If the observed fringe width is 1 cm, what is slit separation distance ? (i.e. distance between the centres of each slit)

The value of g at a particular point is 9.8 m//s^2 Suppose the earth suddenly shrinks uniformly to half its present size without losing any mass. The value of g at the same point (assuming that the distance of the point from the centre of the earth does not shrink) will now be : ..........

In the figure there is a long horizontal bridge over a river 75 m high from water surface. A strong man throws a stone in the parallel plane of the bridge. A observer in a car travelling on the bridge finds the stone going pass by the car while ascending and also while descending between two points on the road 30 m away. The car is travelling at a speed of 15 m/s. The stone is thrown from the bank of river just at the same level of water. Horizontal distance AB travelled by stone is :-

In the figure there is a long horizontal bridge over a river 75 m high from water surface. A strong man throws a stone in the parallel plane of the bridge. A observer in a car travelling on the bridge finds the stone going pass by the car while ascending and also while descending between two points on the road 30 m away. The car is travelling at a speed of 15 m/s. The stone is thrown from the bank of river just at the same level of water. What is the distance between car and atone at the instant when particle reaches at point B ?

A stone is tied to an elastic string of negligible mass and spring constant k. The unstretched length of the string is L and has negligible mass. The other end of the string is fixed to a nail at a point P. Initially the stone is at the same level as the point P. The stone is dropped vertically from point P. (a) Find the distance 'y' from the top when the mass comes to rest for an instant, for the first time. (b) What is the maximum velocity attained by the stone in this drop ? (c) What shall be the nature of the motion after the stone has reached its lowest point ?

A train approaching a hill at a speed of 40 km//hr sounds a whistle of frequency 580 Hz when it is at a distance of 1km from a hill. A wind with a speed of 40km//hr is blowing in the direction of motion of the train Find (i) the frequency of the whistle as heard by an observer on the hill, (ii) the distance from the hill at which the echo from the hill is heard by the driver and its frequency. (Velocity of sound in air = 1, 200 km//hr )