What was Galileo's contribution to the study of motion

What is the force that opposes motion and works against the downward pull? a) friction b) gravity c) weight d) acceleration

Consider a file currently consisting of 200 blocks. assume that the file control block (and the index block in the case of indexed allocation) is already in memory. calculate how many disk i/o operations are required for contiguous, linked, and indexed (single-level) allocation strategies, for each of the conditions listed below. in the contiguous-allocation case, assume that there is not room to grow at the beginning but there is room to grow at the end. also assume that the block information to be added is stored in memory.

If a 250-g mass is hung on two identical springs, hung side by side , and both support the 250-g mass, how much will each spring stretch?