Answer:
-30m/s
Explanation:
Given:
Initial velocity of object = 200 feet/second
Final velocity of object = 50 feet/second
Time of travel = 5 seconds
To calculate acceleration of the object we will find the rate of change of velocity with respect to time.
So, acceleration "a" is given by:

where vf represents final velocity, vi represents initial velocity and is time of travel.
Plugging in values to evaluate acceleration.



The acceleration of the object is -30m/s
Answer:

Explanation:
To solve this exercise it is necessary to take into account the concepts related to gravitational potential energy, as well as the concept of perigee and apogee of a celestial body.
By conservation of energy we know that,

Where,

Replacing


Our values are given by,





Replacing at the equation,


Therefore the Energy necessary for Sputnik I as it moved from apogee to perigee was 
A large amount of molten magnetic material containing Iron is believed to rotate (as a liquid) in the Earth’s core.