the answer is c) the speed and direction of travel must be constant
Answer: The chemical formula for the compound of these two elements is 
Explanation:
For formation of a neutral ionic compound, the charges on cation and anion must be balanced. The cation is formed by loss of electrons by metals and anions are formed by gain of electrons by non metals.
Here metal lead is having an oxidation state of +4 called as
cation and sulphur non metal has oxidation state of -2 called as
. Thus they combine and their oxidation states are exchanged and written in simplest whole number ratios to give neutral 
The chemical formula for the compound of these two elements is 
Rust forms when oxygenreacts with chemicals in rocks, and that is often the case
Answer:
He requires 1 gram of mass.
Explanation:
The density is defined as:
(1)
Where m is the mass and V is the volume.
Then, m can be isolated from equation 1 in order to determine the mass.
(2)
Hence, he requires 1 gram of mass.