Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: vivex_7 on 14/12/2006 19:33:01

Title: What is torque? I find it difficult to visualize it.
Post by: vivex_7 on 14/12/2006 19:33:01

 In a car we need gears to vary the torque. We do so by varying the gear ratio,ie, we vary the angulat velocity.

   T* ω =Power tranmitted which is  assumed constant.

   My question is that if we are supplying same energy,why we need to go on a lower gear to move on a steeper plane.
 

Title: Re: What is torque? I find it difficult to visualize it.
Post by: Soul Surfer on 14/12/2006 20:18:24

Precisely because we are using a constant source of energy.  If we are going up a steeper hill we need a greater supply of energy if we wish go up at the same speed as we did on the level. so we must go up slower.  Internal combustion engines produce more energy as they go round faster (up to a point)  this is because every time the exploding fuel pushes down the piston it gives a similar impulse.  If we need the engine to go round faster and the wheels move slower we need to change gear.

Title: Re: What is torque? I find it difficult to visualize it.
Post by: daveshorts on 15/12/2006 00:34:23

It is basically just about leverage. Torque is a force times a distance.

If you push on the end of a crow bar to lever something out at a speed v and a force F, the force is going to be huge but the speed low:
[diagram=44_0]

If on the other hand you use the same force and speed therefore the same power on the crow bar the other way round you will get a tiny force but huge speed:
[diagram=45_0]

Your car doesn't use levers but gear wheels which do the same thing but in a rotating manner.

So depending on what force you need to apply the gearing on you car (the leverage) should be different.
Going up hill or accelerating fast → low gear
Going on the flat → high gear

Title: Re: What is torque? I find it difficult to visualize it.
Post by: Heliotrope on 16/12/2006 15:20:26

Here's some ancilliary information ...

Car engines are always quoted as developing x amount of horsepower.
In fact engines generate no horsepower at all.
Horsepower is a calculated quantity. You can't measure it directly because the engine isn't producing any.
An engine produces a turning force which is called torque.
Power is r.p.m multiplied by torque.
The power is calculated from the measured value of torque.

Tell your friend with a fast car that his engine produces no power whatsoever and watch him/her go up in flames.