# Science

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a) The centripetal acceleration is related to the planet linear speed and radius of trajectory. This acceleration is continuously changing the direction of the linear speed and thus its direction is towards the center of the circle.

`a_(cp) = v^2/R = 24130^2/(2.28*10^11) =2.554*10^-3 m/s^2`

The centripetal force is then (as Newton second law states):

`F_(cp) =m*a_(cp) =6.42*10^23 *2.554*10^-3 =1.64*10^21 N`

b) Since the centripetal acceleration is towards the circle center, the centrifugal force has the same direction (towards the center of the trajectory).

c) This force comes from the gravitational attraction between the planet and the Sun (all masses attract each other).  Its value is the same as the gravitational force:

`F = G*(m_1*m_2)/R^2 =(6.67*10^11*2*10^30*6.42*10^23)/24130^2 =1.64*10^21 N`

d) Since as said above, all masses attract, this force has everything in common with the force that attracts the objects to the Earth. It is the same gravitational force but this time between Earth and objects.

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