L-10 torque and rotational inertia

Slides:



Advertisements
Similar presentations
Chapter 9 Objectives Calculate the torque created by a force.
Advertisements

Torque Torque is defined as the tendency to produce a change in rotational motion.
L-11 Rotational Inertia Why is a bicycle stable (it doesn’t fall over) only when it is moving? Rotational (angular) Momentum Conservation of angular momentum.
Torque and Rotation Physics.
Circular Motion Terms  The point or line that is the center of the circle is the axis of rotation.  If the axis of rotation is inside the object, the.
L-10(M-9) torque and rotational inertia We consider the rotation of rigid bodies. A rigid body is an extended object in which the mass is distributed.
1 Circular Motion. the motion or spin on an internal axis.
Foundations of Physics
Chapter 9 – Rotational Dynamics
Chapter 9: Torque and Rotation
Torque and Rotational Equilibrium Chapter 8. Torque Rotational equivalent of force Rotational equivalent of force Force isn’t enough to provide a rotation.
AP Physics Torque.
Torques produce rotation in the same way that forces produce motion. HOMEWORK: Read Pg Answer Pg 165 # 7 – 12 Pg 166 (Plug and Chug Questions)
Ch. 11 Rotational Mechanics Torque. TORQUE n Produced when a force is applied with leverage. n Force produces acceleration. n Torque produces rotation.
Torque.
 Point at which all other points on the object rotate around  During motion the CM will move in the same path that a simple particle would move if subjected.
Chapter 8 Rotational Motion.
1.Rotational displacement ‘θ’ describes how far an object has rotated (radians, or revolutions). 2.Rotational velocity ‘ω’ describes how fast it rotates.
Warm-Up: February 17, 2015 Write down a definition for equilibrium.
L-11 Rotational Inertia Why is a bicycle stable (it doesn’t fall over) only when it is moving? Rotational (angular) Momentum Conservation of angular momentum.
Chapter 8 Torque and Rotation  8.2 Torque and Stability  6.5 Center of Mass  8.3 Rotational Inertia Dorsey, Adapted from CPO Science DE Physics.
Torque and Rotation Physics. Torque Force is the action that creates changes in linear motion. For rotational motion, the same force can cause very different.
Objectives  Describe torque and the factors that determine it.  Calculate net torque.  Calculate the moment of inertia.
Motion and Forces in 2 and 3 Dimensions Torque and Rotation.
Center of Mass Torque. Center of Mass When analyzing the motion of an extended object, we treat the entire object as if its mass were contained in a single.
L-10 Torque and Rotational Motion
L-11 Rotational Inertia and Conservation of rotational momentum Why does a wheel keep spinning? Why is a bicycle stable when it is moving, but falls over.
8.2 Rotational Dynamics How do you get a ruler to spin on the end of a pencil? Apply a force perpendicular to the ruler. The ruler is the lever arm How.
8-1 Torque.
Center of Gravity. Definitions Center of gravity (c.g.) = the point located at the center of the object’s weight distribution Center of mass (c.m.) =
Chapter 9 Rotational Dynamics
L-11 Rotational Momentum Why is a bicycle stable (it doesn’t fall over) only when it is moving?
Physics Chapter 8 – Rotational Motion Part 1.
Rotational Dynamics Rode, Kiana, Tiana, and Celina.
L-11 (M-10) Rotational Inertia and Conservation of rotational momentum
TORQUE A torque is an action that causes objects to rotate. Torque is not the same thing as force. For rotational motion, the torque is what is most directly.
REVIEW: TORQUE To make an object rotate, a force must be applied in the right place. the combination of force and point of application is called TORQUE.
Rotational Motion & Torque. Angular Displacement Angular displacement is a measure of the angle a line from the center to a point on the outside edge.
Torque & Center of Gravity
L-10 torque and rotational inertia
L-11 Rotational Inertia Rotational (angular) Momentum
L-11 Rotational Inertia Rotational Momentum Conservation of rotational momentum Why is a bicycle stable (it doesn’t fall over) only when it is moving?
Physics book - Ch 9 Conceptual Book – Ch 11
Torque.
L-10 Torque and Rotational Motion
Circular Motion.
L-10(M-9) torque and rotational inertia
L-10 torque and rotational inertia
Rotational Equilibrium
PHY 131 Chapter 8-Part 1.
Torque.
L-10 Torque and Angular Momentum
Torque and Rotation.
9.1 Torque 1.
Foundations of Physics
Objectives Calculate the torque created by a force.
11.1 Torque To make an object turn or rotate, apply a torque.
L-10 torque and rotational inertia
L-10 Torque and Rotational Motion
Torque.
L-11 Rotational Momentum
L-11 Rotational Inertia and Rotational Momentum
Bell Work: Centripetal Motion
L-11 Rotational Inertia and Rotational Momentum
REVIEW: TORQUE To make an object rotate, a force must be applied in the right place. the combination of force and point of application is called TORQUE.
L-11 Rotational Momentum
9.1 Torque Key Question: How does force create rotation?
L-10 Torque and Rotational Motion
Tor-que? Statics II.
Presentation transcript:

L-10 torque and rotational inertia What does it take to start an object rotating? TORQUE How do I apply a force to make the rod rotate about the axle? Not just anywhere! AXLE

TORQUE [ t (tau)] To make an object rotate, a force must be applied in the right place. the combination of force and point of application is called TORQUE We use the Greek letter, t (tau) for torque lever arm, L Axle Force, F

t = F  L Torque (t) = force (F) x lever arm (L) Force must be in Newtons, N the lever arm length in meters, m then torque in units of Nm

Torque example t = F  L Solution: What is the torque on a bolt applied with a wrench that has a lever arm: L= 20 cm with a force: F = 30 N? F Solution: t = F  L = 30 N  (1/5) m = 6 N m L For the same force, you get more torque with a bigger wrench  the job is easier!

Homer attempts to straighten out the leaning tower of Pisa lever fulcrum

Net Force = 0 , Net Torque ≠ 0 10 N 10 N > The net force = 0, since the forces are applied in opposite directions so it will not accelerate. > However, together these forces will make the rod rotate in the clockwise direction.

Net torque = 0, net force ≠ 0 The rod will accelerate upward under these two forces, but will not rotate.

Balancing torques 20 N 10 N 1 m 0.5 m Left torque = 10 N x 1 m = 10 n m Right torque = 20 N x 0.5 m = 10 N m

Equilibrium  net force = 0  net torque = 0 To ensure that an object does not accelerate or rotate two conditions must be met:  net force = 0  net torque = 0 this results in the practical 4-1 “ladder rule”

When is an object stable? If you can tip it over a bit and it doesn’t fall The object may wobble a bit but it eventually stops and settles down to its upright position. A thinner object is easier to topple An object that is thicker at its base is more stable

Why do tall objects tend to fall over Every object has a special point called the center of gravity (CG). The CG is usually right smack in the center of the object. if the center of gravity is supported, the object will not fall over. The lower the CG the more stable an object is. stable  not easy to knock over!

Condition for stability CG If the CG is above the edge, the object will not fall

when does it fall over? STABLE NOT STABLE CG CG If the vertical line extending down from the CG is inside the edge the object will return to its upright position  the torque due to gravity brings it back. STABLE NOT STABLE

Stable structures Structures are wider at their base to lower their center of gravity

Playing with blocks CG If the center of gravity is supported, the blocks do not fall over

High Profile Vehicles wind As more stuff is loaded into a semi, its center of gravity moves upward, making it susceptible to tipping over in high winds.

rotational inertia (or, moment of inertia), symbol I Rotational inertia is a parameter that is used to quantify how much torque it takes to get a particular object rotating it depends not only on the mass of the object, but where the mass is relative to the hinge or axis of rotation the rotational inertia is bigger, if more mass is located farther from the axis.

rotational inertia examples Rods of equal mass m and length L axis through center axis through end

How fast does it spin? For spinning or rotational motion, the rotational inertia of an object plays the same role as ordinary mass for simple motion For a given amount of torque applied to an object, its rotational inertia determines its rotational acceleration  the smaller the rotational inertia, the bigger the rotational acceleration

Same torque, different rotational inertia spins slow spins fast Big rotational inertia Small rotational inertia spins slow spins fast