 The ability of a force to cause something to turn 9/16 F r = length of lever arm

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

Torque makes it easier to turn things Example: Normally it is 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.

 Turning a wrench  Levers  Trucks  Balances/scales

 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

 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

 Torques can cause objects to rotate either clockwise or counterclockwise.  Clockwise torques (+)  Counterclockwise torques (-) clockwise counterclockwise

F 1 F 2 3 m F 1 will cause the bar to rotate clockwise (+ torque) F 2 will cause the bar to rotate counterclockwise (- torque)

10N 10N 3 m 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.

Will the following object rotate or not? r 2 = 2.5 m r 1 = 3.2 m F 2 = 12 NF 1 = 8 N Determine the torque resulting from F 1  1 = r 1 F 1 = 2.5 *12 = 30 Nm Determine the torque resulting from F 2  2 = r 2 F 2 = 3.2 * 8 = 25.6 Nm

Will the following object rotate or not? r 2 = 2.5 m r 1 = 3.2 m F 2 = 12 NF 1 = 8 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

175 N 7 m5 m 6 m 35 N 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 = r T F T = 5 *35 = 175 Nm Determine the torque resulting from the box’s weight  B = r B F B = 6 *175 = 1050 Nm

175 N 7 m5 m 6 m 35 N 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  3 =  3 = 0  3 = 875 N*m

175 N 7 m5 m6 m 35 N How much do I weigh? 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