Knowing that share prices are determined by the forces of supply and demand, other factors can also play a role in this but lets consider the fact that prices are only based on supply and demand.In this case is it possible for someone to buy a big amount of shares thus making the price rise and then sell them to make a profit ? If so how can the impact on the price be calculated depending on the amount of shares bought ?
What you're failing to consider here is that in buying a large amount of shares, the buyer also makes the price high for himself. And if he sells a large amount of shares at the same time, he's likely to lower the price of the actions while selling them. Poor boy has no chance.