Gravity. The car is heavy and doesnt want to move, so you must excelerate to make the car go uphill. If a car is going downhill, the is no need to excelerate because gravity is pulling the car downhill.
cool
TON -TAN
Because your legs, just like the engine of a car, works best a certain rate of movement and a certain load. A gear that gets you moving easily will have you cranking your legs like crazy w/o getting up to speed while a gear that keeps your legs spinning at a reasonable rate when going fast will be very heavy to turn from a standstill. The ability to change gears allows you to keep pushing with a force and a rythm that suits you, regardless if you're riding on the flat, uphill, or downhill.
Don't really know what you mean by a jump bike... Generally speaking a MTB is intended to be fairly versatile, and it will usually have gears enough both for slow slogs uphill, for going along the flat, and for powering downhill. Something like a dirt bike is usually adapted to run in pretty much one condition only, so taking it on a longer trail with both uphills and descents is likely to be heavy going.
Because car is lighter and has less gravitational force to counter when moving up in comparison to a heavy loaded truck.
Mudflow
Water from the rain mixes with loose sediment, forming a dense slurry that can flow downhill.
I bet it does, because the energy of heavy metal music is bound to make your heart beat faster. It does for me. ;P
Something Heavy Going Down was created in 1984-12.
Fuel Injection. This is controlled by a computer which squirts just the right amount of fuel into the cylinders depending upon what amount is required (more in going faster or uphill or carrying a heavy load). That not only prevents wasted fuel but also helps the engine to run more cleanly, If a catalyst filter is fitted too, this removes or changes the nasty gases coming from the exhaust pipe into otherwise fresh air.
YES