Answer:
From the formula of force:

since AB and k are constants:

x is a constant of proportionality
• when force is 4N, separation distance is 1

therefore, equation becomes

when r is doubled, r becomes 2. find F:

30 grams of radioactive isotope have passed.
Answer:
13
Explanation:
The mass of an atom= number of protons + number of neutrons
Internal combustion engine works by heat. The chemical energy of the fuel turns into heat energy when the fuel is burned, which produces mechanical energy to drive the pistons, to manage the column of the facility and run the vehicle on the road.