# what is the relation between torque and speed?

### 8 Answers

- HandeLv 71 decade agoFavourite answer
For a given capacity the torque is inversely proportional to speed.

As the speed increases torque reduces and vice versa.

- ?Lv 45 years ago
In physics terms, torque is the "tendency to turn" is a force. In more typical language, car and motorcycle enthusiasts refer to "torque" as the power of the engine. This comes from the idea that the engine produces "spin", hence, torque power. As for speed, in physics terms it is a measure of velocity, how fast something is traveling. The relationship between torque and speed can be explained using calculus but suffice to say, the greater the torque of the engine, the more speed can be attained.

- gintableLv 71 decade ago
The formulas work most elegantly with speed measured in radians per second, torque measured in Newton-meters, and power measured in Watts. To hell with horsepower, ft-lbs or whatever else there is in the US Customary system.

Any source of mechanical energy has an upper limit to power output when operated at full power. It can only convert source energy to mechanical energy at a given rate of power.

Because of this, at any point in the transmission, the product of torque and speed equals power (W_dot = tau*omega), and this power is, in an ideal system, equal throughout transmission unless intentionally split to multiple destination shafts.

Gear systems are intended to optimize the transmission for either torque or for speed. Ride any bicycle with gear settings and you will understand. You use reduction gear ratios to climb hills such that you don't wear out your knees trying to output high torque (but instead the gears convert human torque output to higher value needed). Actually in the bicycle case, the lowest gear setting is usually 1:1 with equal input torque as output torque.

Whatever the case of reduction gearing, what you get in torque output, you "pay for" in speed, since the input shaft would need to rotate at faster rates than the output shaft to increase torque.

To optimize for speed, you instead use overdrive gearing. This way the input shaft can run slow, but the output shaft can run fast. You pay for this in torque, because a higher torque is input than is output.

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- Racer XLv 41 decade ago
In general, the greater the torque your car generates, the faster you can accelerate. Torque really has nothing to do with top speed though - higher torque will get you to your top speed quicker though.

- EckoLv 71 decade ago
Power is torque x speed. A formula is:

Power_W = (torque_N.m x 2pi x RPM) / 60

The torque is in newton meters here. Use an on line calculator to convert to other units such as foot pounds..

- 1 decade ago
Its all to do with gear ratio.

With a slower gear will give better torque and a faster gear will have less torque but faster speed.

- mukesh mahadeoLv 51 decade ago
for certain power transmission, greater torque reduces speed and vice versa.