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Quick Quiz On Gravitation
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Give all answers to
3s.f. unless otherwise asked.
Re = 6400km
Me = 6.00*1024 kg
G = 6.67*10-11
Nm2kg-2
c = 3.0*108 m/sec
1. Calculate
the orbital speed of the earth (to the nearest km/sec) if it is at an average
distance of 1.5*108 km from the sun.
km/sec
2. If the
mass of the earth is as given above
(a)
Calculate the height above the earth's surface that a geostationary satellite
will orbit in free-fall.
x103
km
(b) The
acceleration of free fall at an altitude of 2000km.
m/sec2
3. If the
mass of a proton is 1.67 * 10-27kg and an electron is
9.1*10-31kg, and the Bohr radius of a hydrogen atom is 5.30*10-10m
(a)
calculate the gravitational force of attraction between them..
*10-49
MeV
(b) The
orbital 'speed' of the electron due to this force.
x
10-14m/sec
4. A black
hole forms if the escape velocity of the parent body exceeds the speed
of light.
(a)
What radius would the sun have to be if it were to form a black hole (without
losing any mass) ?
km
(b) Repeat
for the earth.
mm
5. Calculate
the escape velocity of the earth.
km/sec
6. A spy
satellite is to be placed in orbit at a height of 15000 km above the surface
of the earth.
(a)
Calculate its orbital speed.
km/sec
(b) What
is the time period of its orbit ?
hours
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