The acceleration due to gravity serves as the centripetal acceleration of the objects that orbits the Earth. The centripetal acceleration due to gravity is calculated through the equation,
a = v²/r
where v is the speed and r is the radius. Substituting the known values to the equation,
9.8 m/s² = (420 m/s)² / r
The value of r from the equation is 18000 m or equal to 18 km.
<em>Answer: 18 km</em>
Explanation:
A charge alters the space around it. This alteration of space is called the electric field. It is also defined as the electric force acting on a charged particle per unit test charge. It is given by :

Where
F is the electric force, 
The direction of electric field is in the direction of electric force. For a positive charge, the direction of electric field lines are outwards and for a negative charge, the direction of field lines are inwards.
Hence, the correct option is (c) "electric field".
Answer:
5 sq. root 3
Explanation:
theta= 60°
=> u sin theta = 10 × sin 60
= 10× sq. root 3/2
= 5 sq. root 3
Answer:
2.5
Explanation:2.5 +2.5 = 5.0