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Torque

Torque (τ; Greek letter "Tau") is the measurement unit of the force causing what turns to rotate around a point, often measured in pound-foot.

Note: Though torque and pound foot are at times interchangeable. "Pound-foot" (lb⋅ft) is a unit of torque, a twisting force that causes rotation. "Foot-pound" (ft⋅lb) is a unit of energy or work, representing the work done by a force acting over a distance. While both are expressed as a product of pounds and feet, they represent different physical quantities.

Pound foot

Note: Not confuse "pound-foot" with "foot-pound."

E.g. Consider a wrench around a seized up nut:
Using a small wrench is hard to free the nut.

Longer wrench is easier--due to torque.

With a short 30 cm wrench with 90 N force, we get 0.3m*90N = 27 Nm

With a longer 60 cm cm at 90N as well, it's 0.6m*90N = 54 Nm

So, a longer wrench is easier to rotate it, basically using a bigger circle to turn a smaller one (Fig 1).

Fig 1

Fig 2

A low gear gives speed but high torche. A high gear gives high speed but low torche.

It's hard to ride a bike with high gear (Fig 3), so a lower gear (Fig 4) is easier to ride it.

But as we can't go faster, change the wheel to another higher (medium) gears (Fig 5).

Fig 3

Fig 4

Fig 5

Fig 6

Upon reaching a steep hill, we need a lower gear, same as cars (Fig 7).

Fig 7

Conversions

Torque in ounce inches,

T = F*3.6*6” = ounce-inches

T = Torque in ounce-inches
F = force in Newtons
D = radius in inches (6”)

[4] Newton (N): amount of force needed to accelerate 1 kg mass by 1m each second (1m/s).

N = 1kg*m/s² = [1 kg*(m/s)]/s

Some forces are calibrated in Netwons:

To convert Newton to ounces, multiply it by 3.6. A lab prony brake arm's radius is 6'':

Formula: T = FD

T = torque in pound-feet
F = force in pounds
D = distance/radius in feet

Calculations for AC Motors:

T = KV2

T = torque
V = voltage
K = a motor's constant

To convert ounce-inches to pound-feet, as 16 ounces are in a pound, and 12 inches in a foot,

divide ounce-inches by (16 x 12) or ounce-inches ÷ 192.

Power

Power factor:

References

[1] What is Torque? - Torque basics explained - YT
[2] Wikipedia
[3] Foot-pound (energy) - Wikipedia
[4] What is a Newton - YT
[5]
[7]

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