1.) The small spherical planet called \"Glob\" has a mass of 6.8e+18 kg and a ra

Question

1.) The small spherical planet called "Glob" has a mass of 6.8e+18 kg and a radius of 62000 m. An astronaut on the surface of Glob throws a rock straight up. The rock reaches a maximum height of 1800 m, above the surface of the planet, before it falls back down. What was the initial speed of the rock as it left the astronaut's hand? (Glob has no atmosphere, so no energy is lost to air friction.) (G = 6.67 x 10-11Nm2/kg2)
(in m/s)

2.) A star of mass 1.69×1031 kg and diameter 7.70E+9 m rotates with a period of 25.0 days. Suddenly the star changes size, and rotates with a new period of 16.0 days. Assuming a uniform density both before and after the size change, what is the new diameter of the star?

DATA:

(in m)

3.) Find the speed of a satellite in a circular orbit around the earth with a radius 2.15 times the mean radius of the earth; Radius of earth= 6.37·103 km; Mass of earth= 5.98·1024 kg. (in m/s)

Explanation / Answer

Applyconservation of energy

PEi + KEi = PEf + KEf

since final kinetic energy is zero

-Gm1m2/r1 + ( 1/2 )mvi2 = -Gm1m2/r2

-Gm2/r1  + ( 1/2 )vi2= -Gm2/r2

-( 6.67* 10^-11 )( 6.88 10^18 kg ) / 6200 m+ ( 1/2)v12 =-( 6.67* 10^-11 )( 6.88 10^18 kg ) / 6200 m+1800 m

-74015.48 +  1/2)v12=-57362 m/s

v1 = 182.5 m/s

As per guide lines I worked first problem

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