Torque

torque 

• def: the tendency of a force to rotate an object

• SI units: Nm

• force that causes rotation: 

  • the point of application matters

  • the direction matters 

• *only the perpendicular component of the force (F⊥) causes it

  • F⊥ = Fsin(θ) 

• Magnitude: t = rF⊥ = rFsin(θ)

• direction: clockwise(-) or counterclockwise (+)

torque is a vector quantity (direction matters)

remember: torque is a vector quantity (direction matters) 

t = rF⊥ = rFsin(θ)

what is the equation to find the magnitude of torque (t)?

the tendency of a force to rotate an object  

what is the def of torque (t)?

only the perpendicular component of the force (F⊥) causes torque

remember: only the perpendicular component of the force (F⊥) causes torque

F⊥ = Fsin(θ) 

what is the equation for the perpendicular component of the force (F⊥)?

the parallel component of the force is useless / causes no torque

remember: the parallel component of the force is useless / causes no torque

r

• the distance from the pivot point to the point where the force is applied

• the larger it is the more torque there is

the distance from the pivot point to the point where the force is applied

what is r?

the larger r is the more torque there is

remember: the larger r is the more torque there is

ropes always leave the pulley at a 90° angle to the radius (this is ALWAYS true for problems involving ropes on pulleys)

remember: ropes always leave the pulley at a 90° angle to the radius (this is ALWAYS true for problems involving ropes on pulleys)

when torque directions are opposite from each other (ex: counterclockwise and clockwise) you DO NOT add to get the net torque, you subtract smaller # from bigger # and end direction is the direction of the bigger 3

remember: when torque directions are opposite from each other (ex: counterclockwise and clockwise) you DO NOT add to get the net torque, you subtract smaller # from bigger # and end direction is the direction of the bigger 3