Which is most likely a physical change

a. cutting a substance into four pieces
b. burning a substance into ash and smoke
c. reacting a substance chemically to form a new substance
d. combining a substance with water to make rust

The diagram shows four locations in the electric field of a positive point charge m. at which location is the electric potential the greatest.

Question part points submissions used suppose that 2 j of work is needed to stretch a spring from its natural length of 26 cm to a length of 36 cm. (a) how much work is needed to stretch the spring from 28 cm to 32 cm? (round your answer to two decimal places.)

Estimate the schwarzschild radius (in kilometers) for a mini-black hole formed when a superadvanced civilization decides to punish you (unfairly) by squeezing you until you become so small that you disappear inside your own event horizon. (assume that the your weight is 50 kg)