### Class XI

The total energy of a circularly orbiting satellite is
1. positive small
2. negative
3. positive large
4. zero
If the radius of earth reduces by 4% and density remains same then escape velocity will
1. Increase by 4%
2. Reduce by 4%
3. Increase by 2%
4. Reduce by 2%
Deimos, a moon of Mars, is about 12 km in diameter with mass 2.0 ×× 10151015 kg. Suppose you are stranded alone on Deimos and want to play a one-person game of baseball. You would be the pitcher, and you would be the batter! You have to throw a baseball so that it would go into a circular orbit just above the surface and return to you so you could hit it. How long (in hours) after throwing the ball should you be ready to hit it?
1. 2.03 hr
2. 2.11 hr
3. 2.35 hr
4. 2.20 hr
A satellite orbits the earth at a height of 400 km above the surface. How much energy must be expended to rocket the satellite out of the earth’s gravitational influence? Mass of the satellite = 200 kg; mass of the earth = 6.0 ×× 1024 kg; radius of the earth = 6.4 ×× 106 m; G = 6.67 ×× 10​​​​​​​-11 N m2 kg​​​​​​​-2.
1. 6.5 ×× 109109 J
2. 6.2 ×× 109109 J
3. 5.9 ×× 109109 J
4. 6.0 ×× 109109 J
Consider a spacecraft in an elliptical orbit around the earth. At the low point, or perigee, of its orbit, it is 400 km above the earth’s surface; at the high point, or apogee, it is 4000 km above the earth’s surface.It is necessary to have the spacecraft escape from the earth completely. If the spacecraft’s rockets are fired at perigee, by how much would the speed have to be increased to achieve this?If the spacecraft’s rockets are fired at apogee, by how much would the speed have to be increased to achieve this?
1. 5410 m/sec(perigee),8761 m/sec(apogee)
2. 4410 m/sec(perigee),7761 m/sec(apogee)
3. 3410 m/sec(perigee),6761 m/sec(apogee)
4. 2410 m/sec(perigee),8761 m/sec(apogee)
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