The scientific notation should specific the significant digits. So it to write like x.xx * 10 ^ x. So the answer is 6.421 * 10 ^3.
I think the answer would be 1.58 g.
For machines such as a rake the output force is less than the input force. If the input force of the rake is 10 newtons and the output force is 5 Newtons mechanical advantage is .5
