41.
Which planet has the lowest density?

42.
The sensation of weightlessness in a spacecraft in an orbit is due to the

43.
The different colours of different stars are due to the variation of

44.
Which of the following is correct about the properties of Gravitational Forces?

45.
In the absence of the earth's atmosphere, sky would appear

46.
We always see the same face of the moon, because

47.
The fact that the planets move around the Sun, not in circles but in ellipses, was first demonstrated by

48.
A bomb explodes on the moon. You will hear its sound on earth after ________

49.
Stars are held together by

50.
The minimum number of geostationary satellites needed for uninterrupted global coverage is :