Why a spacecraft consume more fuel in going from earth to moon than it does on the return trip ?

A spacecraft consume more fuel in going from earth to moon than it does on the return trip. Comment on this.

Ans.     In going from earth to moon, the spacecraft has to do more work against the greater gravitational attraction of the earth. For the return journey, moon’s gravitational force is much less, hence less work is done and less fuel is consumed.

Why are space crafts usually launched from west to east?

Why are space crafts usually launched from west to east? Why is it more advantageous to launch rockets in the equatorial plane?

Ans.     Earth rotates on its axis from west to east. A satellite launched from west to east will have the advantage of the additional velocity of the earth’s rotation. The effect is maximum  at the equator, hence it is most advantageous to launch the satellite from west to east on the equatorial plane.

What is the Reasons For Weightlessness ?

Reasons For Weightlessness :
Sol: 1. Any artificial satellite itself in a state of weightlessness condition becomes total earth gravitational force is balanced by centripetal force in order to orbiting the satellite in the given stable orbital.
2. Weightlessness conditions for any body placed inside the satellite can be employed in the following ways :
(a) Centrifugal force experienced by inside the body is neutralized by earth gravitational force.
(b) There is no normal reaction experienced by body from the surface to satellite because it is treated as point mass.
(c) Any body having zero relative acceleration with respect to satellite.

Why are there holes in the sides of a sounding box ?

Scientific Reasoning :Why are there holes in the sides of a sounding box ?

Sol: The energy of the air inside the box is dissipated to the outside air  . This prevents the possible resonant vibration of sounding box . Resonant vibration of the box is not desirable
because it shortens the duration of emission . This is why holes are provided in the sides of a sounding
box .

Why are soldiers ordered to break steps while crossing a bridge ?

Scientific Reasoning : Why are soldiers ordered to break steps while crossing a bridge ?

Sol:While crossing a bridge , if the period of stepping on the ground by marching soldiers be equal to the natural frequency of the bridge , it may be thrown into resonance vibration and the vibrations may be so large that the bridge may collapse .Thus to avoid resonant vibration of the bridge , soldiers are ordered to break steps .