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Torque Principles of Physics

Torque Principles of Physics. 9/16. TORQUE. The ability of a force to cause something to turn. F. r = length of lever arm. Torque. Equation  = r *F. Symbols/units  = Torque (N*m) r = length of lever arm (m) F = force (N). Why is torque important.

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Torque Principles of Physics

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  1. TorquePrinciples of Physics

  2. 9/16 TORQUE • The ability of a force to cause something to turn F r = length of lever arm

  3. Torque Equation  = r *F Symbols/units  = Torque (N*m) r = length of lever arm (m) F = force (N)

  4. Why is torque important Torque makes it easier to turn things Example: Normally itis difficult to loosen a nut or bolt by hand. • A wrench does not make you any stronger, but it increases your turning ability. • The farther a force is applied from the nut, the greater the torque it produces.

  5. Everyday applications • Turning a wrench • Levers • Trucks • Balances/scales

  6. Example • A force of 20 N is applied to the end of a wrench that is 0.2 m long. What is the torque that is produced in this situation?  = r *F • = 0.2 m * 20 N • = 4 N*m

  7. Rotational Equilibrium • More than one torque can act on an object at one time. • In order for the object not to spin, the torques must be balanced • When torques are balanced they add up to zero

  8. Torque is a vector • Torques can cause objects to rotate either clockwise or counterclockwise. • Clockwise torques (+) • Counterclockwise torques (-) counterclockwise clockwise

  9. 3 m 3 m F1 F2 F1 will cause the bar to rotate clockwise (+ torque) F2 will cause the bar to rotate counterclockwise (- torque)

  10. 3 m 3 m 10N 10N The rod will not rotate because the torque that makes the object want to rotate clockwise is balanced by the torque that makes it want to rotate counter-clockwise.

  11. Example 1 Will the following object rotate or not? r2 = 2.5 m r1 = 3.2 m F1 = 8 N F2 = 12 N Determine the torque resulting from F1  1 = r1F1 = 2.5 *12 = 30 Nm Determine the torque resulting from F2  2= r2F2= 3.2 * 8 = 25.6 Nm

  12. Example 1 Will the following object rotate or not? r2 = 2.5 m r1 = 3.2 m F1 = 8 N F2 = 12 N Object won’t rotate if net torque = 0  1+  2= 0?  1 +  2=  net 25.6 – 30 =  net -4.4 N*m =  net Object will rotate counterclockwise

  13. See-saw Example 35 N 175 N 6 m 7 m 5 m A man, a turtle, and a box are positioned on a giant see-saw as shown. If the see-saw doesn’t rotate, what torque must the man produce? Determine the torque resulting from the turtle’s weight  T= rTFT= 5 *35 = 175 Nm Determine the torque resulting from the box’s weight  B= rBFB= 6 *175 = 1050 Nm

  14. See-saw Example 35 N 175 N 6 m 7 m 5 m A man, a turtle, and a box are positioned on a giant see-saw as shown. If the see-saw doesn’t rotate, what torque must the man produce? Net Torque = 0  T +  B +  M=  net -175 + 1050 -  3 = 0 875 -  3 = 0  3 = 875 N*m

  15. How much do I weigh? See-saw Example 35 N 175 N 7 m 5 m 6 m A man, a turtle, and a box are positioned on a giant see-saw as shown. If the see-saw doesn’t rotate, how much must the man weigh? • = rF • 875 = (7)F • F = 125 N

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