Answer:
(a)
M = 1.898 x 10^27 kg
(b)
v = 13.74 km/s
(c) E = 0.28 N/kg
Explanation:
Time period, T = 3.55 days = 3.55 x 24 x 3600 second = 306720 s
Radius, r = 6.71 x 10^8 m
G = 6.67 x 10^-11 Nm^2/kg^2
(a) 


M = 1.898 x 10^27 kg
(b) Let v be the orbital velocity


v = 13739.5 m/s
v = 13.74 km/s
(b) The gravitational field E is given by


E = 0.28 N/kg
To solve this problem we will apply the concepts related to the calculation of the speed of sound, the calculation of the Mach number and finally the calculation of the temperature at the front stagnation point. We will calculate the speed in international units as well as the temperature. With these values we will calculate the speed of the sound and the number of Mach. Finally we will calculate the temperature at the front stagnation point.
The altitude is,

And the velocity can be written as,


From the properties of standard atmosphere at altitude z = 20km temperature is



Velocity of sound at this altitude is



Then the Mach number



So front stagnation temperature



Therefore the temperature at its front stagnation point is 689.87K
The colder the more likely it is to become a liquid
The train is moving at 50 m/s and Emma is walking down the aisle with 1 m/s speed in the same direction of train. The relative velocity of Emma with respect to other passengers pf the train would be 1 m/s. This is because, the train is not moving relative to them and only emma is moving at 1 m/s. If a person observes from outside, Emma would have (50 +1) m/s = 51 m/s velocity.
relative velocity when two objects are moving in same direction as oberved from outside observer:

relative velocity when two objects are moving in the opposite directionas oberved from outside observer:
