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Torque. Chapter 8 Section 1. Rotational and Translational Motion. The complicated motion of any object, or objects, can be described in rotational and/or translational motion. Translational (linear) Motion – The movement that changes the position of an object.
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Torque Chapter 8 Section 1
Rotational and Translational Motion • The complicated motion of any object, or objects, can be described in rotational and/or translational motion. • Translational (linear) Motion – The movement that changes the position of an object. • Rotational Motion – The movement that cause an object to rotate around an axis. • For this section on torque, we will focus on rotational motion.
Torque Produces Rotation • Torque can be seen in many different areas in the real-world. • Vehicles • Doors • Wrench • Etc… • Anything that rotates when a force is applied to the object.
Torque • Torque – A quantity that measures the ability of a force to rotate an object around some axis.
Torque Depends on a Force and a Lever Arm • The more force applied to an object to make it rotate, the more torque is formed. • The longer the distance away from the axis of rotation, the more torque applied. • Example: Lets look at a door F d Axis of Rotation
Lever Arm • Lever Arm – The perpendicular distance from the axis of rotation to a line drawn along the direction of a force. • What’s better for loosening a rusty nut? • Your hand or a wrench? Why?
Torque Depends on Angle of Force • The torque also depends on the angle between a force and the lever arm. • The greatest amount of torque produced is when the force is perpendicular to the lever arm.
Torque Equation T = Fd(sinθ) • T = Torque - Greek Letter “tau” • F = Force • d = Length of lever arm • θ = The angle between the force and lever arm
SI Units of Torque • The SI units for torque are: Newton•meters N•m • Standard units seen here in good old America: Foot•pounds
The Sign of Torque • A torque can be positive or negative depending on the direction of rotation produced by the force. • Clockwise rotation – NEGATIVE torque • Counter-Clockwise rotation – POSITIVE torque
More Than One Force • If more than one force is being applied to a single lever arm, each force that produces a torque is treated separately. • The sum of the torques on the lever arm will give the net torque acting on the lever arm. Tnet = ΣT = T1 + T2 + … • Make sure to label the correct sign to each torque
Example Problem #1 • A mechanic pushes at an angle of 85 degrees on the end of a 0.30ft wrench. If the mechanic applies a force of 105N, what is the torque applied on the bolt?
Example Problem Answer #1 • T = 9.41 Nm
Example Problem #2 • Two masses are on a seesaw on opposite sides of the pivot point. On the left side of the seesaw a 15kg mass is sitting 2.5m away from the pivot point. How far away from the pivot point would a mass of 10kg be placed on the right side of the seesaw for the seesaw to be perfectly balance? 15kg 10kg d2 = ? d1 = 2.5m
Example Problem Answer #2 • d2 = 3.75m