The planets revolving around the sun, The moon revolving around the Earth.
Answer:

Explanation:
Electric field in a given region is given by equation

as we know the relation between electric field and potential difference is given as

so here we have


here we know that
and 
so we will have

so we will have

Answer:
10 km/hr/s
Explanation:
The acceleration of an object is given by

where
v is the final velocity
u is the initial velocity
t is the time
For the car in this problem:
u = 0

t = 6 s
Substituting in the equation,

Answer:
i think the answer is gravity