Quote:
Originally Posted by CyberFormula
Torque in a truck is high so the engine can turn...and hull stuff.
But their acceleration isn't HIGH because they're heavy usually.
High torque may transfer as high acceleration, but like a previous member said, it depends on other factors.
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That is because of gearing. Think about riding a bike. Your legs generate a certain force which pushes on the pedals. The pedals turn that force into torque on the gears, which multiply the force and then apply it to the bike wheel. In low gears, the torque is multiplied by >1 (let's call it 2, not realistic but bear with me) which results in every lb/ft of force on the pedals generating 2 lb/ft on the wheel, but only 1/2 the distance (if you move your leg 6" the wheel only moves 3"). That force will accelerate the bike at a certain rate based on apparent weight (which would be higher going up a hill, or lower going down a hill), wind resistance, and friction in the chain/gears/bearings. Your legs are able to create that force up to a certain pedal speed, at which point you shift gears to get a gear with lower torque multiplication, but higher speed. You will then continue to accelerate because the inertia is less since you are now moving, but you won't accelerate as quickly as before because torque is reduced. If you could pedal at infinite speed you could always be in the lower gear and accelerate instantly. Your ability to generate force at a certain pedal speed is HP by the way.
When choosing gearing, you basically have a choice between ability to turn stuff (torque) and speed at which you are turning (rpm). Let's say you had the same engine in a truck and a car. The truck would choose gears with higher torque multiplication but less acceleration. The car would choose gears with higher acceleration but lower torque multiplication. If both vehicles weighed the same, the car would accelerate faster, assuming the engine was powerful enough to overcome inertia. But, once you added more weight (say attached a trailer), the car would just bog down because there wouldn't be enough torque to overcome the inertia. In this case the truck would accelerate faster. So, to expand on my previous post, torque causes acceleration, unless it is overcome by inertia. You can think of a free body diagram with torque causing a force on a wheel in one direction (say counterclockwise) and inertia going the other direction (clockwise). The extent to which torque is greater than inertia determines the amount of acceleration, but eventually you run out of engine speed and must change gears, so if you have too much torque (cause by having truck like gears) you will end up accelerating slower because every rotation of the crankshaft results in less rotations of the wheels. I hope that made sense...