Answer:
a) a = 5.03x10¹³ m/s²
b) 
Explanation:
a) The acceleration of the positron can be found as follows:
(1)
Also,
(2)
By entering equation (1) into (2), we have:

<u>Where:</u>
F: is the electric force
m: is the particle's mass = 9.1x10⁻³¹ kg
q: is the charge of the positron = 1.6x10⁻¹⁹ C
E: is the electric field = 286 N/C
b) The positron's speed can be calculated using the following equation:

<u>Where</u>:
: is the final speed =?
: is the initial speed =0
t: is the time = 8.70x10⁻⁹ s

I hope it helps you!
A 5kg backpack will weigh 49 newtons on earth
Huh??????????????????????????
Answer:
The gravitational force between them increases by a factor of 4
Explanation:
Gravitational force is a force of attraction between two objects with masses M and m which are separated by a distance R. It is given mathematically as:
Fg = GMm/R²
Where G = Gravitational constant.
If the distance between their centers, R, decreases by a factor of 2, then it means the new distance between their centers is:
r = R/2
Hence,the gravitational force becomes:
Fg = GMm/r²
Fg = GMm/(R/2)²
Fg = GMm/(R²/4)
Fg = 4GMm/R²
Hence,the gravitational force increases by a factor of 4.