Chopping solid vegetables in a blender is not much like liquid blending, so all of these estimates are at best just estimates.  A four-blade impeller with sharp blades will not have much resistance in a well copped and dispersed mixture, but could encounter much more resistance cutting through solid vegetables.  The amount of resistance at the low speed will be very different depending on whether the vegetables are carrots (firm) or tomatoes (soft).
 
As some general rules, based on fluid mixing, the torque required at 2000 rpm will more than 1500 times the amount of torque required at 50 rpm.  So the actual range of torques can be quite different.  Kitchen experience with food choppers says that the torque at low speeds can be quite high because of the resistance in cutting solid vegetables, although I don't ever remember seeing a chopper that operated at only 50 rpm. 

At that speed, you can see the blade rotating at less than one revolution a second.
 
Using a range of experience and process knowledge, I estimate that the maximum torque in a mixed vegetable blend at 2000 rpm could be roughly 0.5 Newton-meters.  If the chopped vegetables form a very heavy slurry, the torque could increase to 1.5 Newton-meters.  Those values are only rough estimates based on an educated guess at both the processed food properties and the power characteristics of a four-blade chopper.

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