Hat are three machines or devices that depend on gravity to work?

you're giving away points because you can't type stuff out.

explanation:

given the lack of choices, i'm gonna wing it and say that pushing your car off a cliff might not be the best idea. your car might sustain damage from the fall and will probably result in the car being too damaged to jump start.

if that's not good enough, avoid filling the car with bees. bees might get agitated when trapped or during the moving process, and might result in death or painful stings that will make jump starting your car very difficult. but in the event that you do choose to fill your car with bees, remember to wear protective gear!