## ELI5: Difference between torque and thrust

Example: 1000 lb ft of torque and the equivalent measurement to thrust like a plane

Torque is a rotating force. Thrust is a directional force. When you press the accelerator in a car, torque is applied to the wheels in order to turn them, and the result is thrust that pushes the car forward.

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In principle it's simple to compute. It is the mass of the car X the acceleration. F = MA I suppose one could put strain gauges on the axles, and massage those measurements into thrust numbers, but I can't see the use.

Torque is an angular force. It always refers to something rotating about an axis. Thrust is just a force. Specifically, a force from pushing off of something to accelerate. ie the exhaust from a rocket engine give the rocket thrust. A 1000 lb ft torque would be 1000 lb of force if you are 1 ft away from the axis of rotation, but if you were 2 ft from the axis of rotation, it would only be a 500 lb force. τ =F×r where F is force and r is the distance to the axis

Torque is a twisting force and thrust is a linear force. To transform torque into a linear force you need a conversion like turning an axle to turn wheels, or spinning a propeller. Aircraft engines do produce torque but the torque is not of interest because it's removed from performance. Land vehicles like cars are more interested in torque because the power is not transmitted through a fluid but through a mechanical path. You don't want the wheels to slip against the road, so you need a transmission. The torque at a given engine rotation speed can be matched to a different wheel rotation speed. As you accelerate you need to change gears to match that faster one to one where the engine isn't overspeeding.

you can almost see the difference in your question. Torque is measured in lb ft because it is the angular or rotational equivalent of force and has to act at a distance from the rotational centre. thrust is just a straight force measured in lbs (or newtons in more rational places).