Can someone me with 8 & 9? i took a guess but i'm not too sure, ty

For number 8, it all depends on the situation. For example, if you have short people and tall people race each other their height won't effect their speed; it all depends on skill. So this is a yes or no question based on the situation.

For number 9, I believe you're right for this question as well. For example, if you increase the height of a ramp then the speed of the car will increase most likely.

Mitochondria produce atp, a high energy compound. atp is used for all sorts of enzyme-mediated reactions, such as making proteins/nucleotides/etc, certain compounds cross the cell membrane, muscles move, etc.  without this source of energy, a cell will die. it will not be able to repair itself, defend against pathogens, etc.