i. Earth's gravitational force of the attraction vanishes at




... Answer is (b)  infinity
According to the law of gravitation, the force of attraction between two mass directly proportional to the product of their masses and is inversely proportional to the square of the distance between their centers. So as the distance increase the gravitation force becomes weaker and weaker. when the distance becomes infinity. Something divided by an infinity square is almost ZERO. So Earth's gravitational force of the attraction vanishes at infinity.


ii. Value of g increases with the




... Answer is (b) a decrease in altitude
The formula to find g=GM/(r+h)2. It is clear that the value of g is inversely proportional to the distance of the body from the centre of the earth. Its value is maximum (9.8 ms^-2) at the surface of the earth at mean sea level. The value of g decreases with the increase in altitude. The value g is equal to 9.5 ms^-2 at 100 km altitude. The value of g increases with the decrease in altitude is the right answer.


iii. The value of g at the height of one Earth's radius above the surface of the Earth is




... Answer is (d) 1/4 g
The formula to find g=GM/(r+h)2. The value of g at the height of one Earth's radius above the surface of the Earth g=GM/(r+r)2 = 1/4 g


iv. The value of g of g on the moon's surface is 1.6 ms-1. What will be the weight of a 100 kg body on the surface of the moon?




... Answer is (b) 160 N
 Weight W = mg here m =100 kg and g = 1.6 ms^-2 so W = 100 kg x 1.6 ms^-2 W = 160 N


v. The altitude of geostationary orbits In which communication satellites are launched above the surface of the Earth is:




... Answer is (d) 42,300 km
The altitude of geostationary orbits In which communication satellites are launched above the surface of the Earth is 42,300 km.


vi. The orbital speed of a low-orbit satellite is : 




... Answer is (d) 8000 ms^-1
The mean orbital velocity needed to maintain a stable low Earth orbit is about 7.8 km/s (~ 8000 m/s) = (28,000 km/h or 17,000 mph)



VIP Note: If you have Learned the above MCQs, then examine yourself by taking this Simple MCQS Quiz (Click here to play the Quiz)

 

Unit-5: Gravitation
⇑
9th Class MCQs Quizzes LIST

⇑
Unit-4     ⇚  9th Physics Content List   ⇛  Unit-6

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