Monday, February 27, 2017

Activity 88:Conservation of Angular Momentum






Linear Momentum = mv


Angular (Rotational) Momentum  = (I)(Angular Velocity)

Conservation of Momentum holds true for both.

mv before = mv after

Angular Momentum Before = Angular Momentum After


Seminar Skater Problem


Do Problems 38 through 41 at the end of chapter 10

Check your answers here

Thursday, February 16, 2017

Activity 87: Rotational Kinetic Energy





Derivation of Rotational Energy Equation


net W  = (net F )Δs 

net W  = (r  net F )Δs/r 

net W  = (net τ)θ 


 net τ = Iα

 net W  = Iαθ

























Consider a person who spins a large grindstone by placing her hand on its edge and exerting a force through part of a revolution . In this example, we verify that the work done by the torque she exerts equals the change in rotational energy.

(a) How much work is done if she exerts a force of 200 N through a rotation of 1.00 rad(57.3º) ? The force is kept perpendicular to the grindstone’s 0.320-m radius at the point of application, and the effects of friction are negligible.


(b) What is the final angular velocity if the grindstone has a mass of 85.0 kg?


(c) What is the final rotational kinetic energy? (It should equal the work.)

Assignment:

Do Problems 21, 22,23,24,25, 27 & 28 on page 357 in the textbook.
 When you are done check your answers here.

Complete this worksheet

When done check your answer here.

Tuesday, February 14, 2017

Activity 86: Introduction to Moment of Inertia






Moment of Inertia:






mr2 is called the moment of inertia  - the resistance of a mass a distance r to a change in its angular acceleration.


This is analogous to the way that inertial mass resists translational acceleration.


Inertial Mass (m) and  Moment of Inertia (I) resist translational and angular acceleration.








Consider the father pushing a playground merry-go-round.  


He exerts a force of 250 N at the edge of the 50.0-kg merry-go-round, which has a 1.50 m radius.  (Consider the merry-go-round itself to be a uniform disk with negligible retarding friction.)


Calculate the angular acceleration produced:


(a) when no one is on the merry-go-round


(b) when an 18.0-kg child sits 1.25 m away from the center. Consider the merry-go-round itself to be a uniform disk with negligible retarding friction.




Activity 82.10
Problems 10 -> 15 on page 356.

When done  check your answers here..






Friday, February 10, 2017

Activity 85: Rotational Kinematics

Rotational (Angular) Kinematics is similar to Linear (Translational) Kinematics


Our previous knowledge of translational kinematics and motion can be extended to describe rotational kinematic motion.


A radian 𝚹 in rotational kinematics is analogous  to displacement in linear (translational) kinematics


When linear distance, (d,s,x,etc…), was measured, we used meters or similar metric unit.  Now we must use radians to measure angular or rotational distance, θ.


A radian “𝚹” is analogous  to a meter


Thus an angle will be analogous to distance .
Screenshot 2015-01-01 17.47.57.png


Relationship
s = rRotational (Angular) Kinematics is similar to Linear (Translational) Kinematics


Our previous knowledge of translational kinematics and motion can be extended to describe rotational kinematic motion.

A radian 𝚹 in rotational kinematics is analogous  to displacement in linear (translational) kinematics

When linear distance, (d,s,x,etc…), was measured, we used meters or similar metric unit.  Now we must use radians to measure angular or rotational distance, θ.

A radian “𝚹” is analogous  to a meter

Thus an angle will be analogous to distance .

Screenshot 2015-01-01 17.47.57.png

Relationship

s = r𝚹
 𝚹 = s/r

Activity 85.10

Read Section 10.1 in the textbook.
Pick up a copy of this Seminar Problem 1 and complete.


Activity 85.20

Pick up a copy of this Angular Motion & Acceleration Worksheet and complete. When done check your answers here.


The equations and concepts you learned in Translational Kinematics have an analogous relationship to Rotational Kinematics. 







Activity 85.30  




Activity 85.40

- Do problems 5-9 on page 356 in the textbook.   When you are done check your answers here.

  





Sunday, February 5, 2017

Activity 83: Slipping and Tipping and Stability

A



With a lab partner read and execute this Slipping and Tipping Activity.  It is on pages 72 - 73 in the lab book.  This is not a formal lab write-up.  Simply do the exercises and answer the "light-bulb" questions on paper ( per group)  and hand it in.


Thursday, February 2, 2017

Activity 82: Center of Mass Lab Activity



Go to this Google Classroom Activity and read and complete the Center of Mass Assignment

The important part of this assignment is a well documented procedure.  Be sure to put all team names on the submission.

Activity 81: Solving Force & Torque Equilibrium Problems

Activity 81.10

Watch this video on solving torque and force problems.





Activity  81.20

Pick up a paper copy of this worksheet and solve.  When you are done please check your answers here.

Wednesday, February 1, 2017

Activity 80: Center of Gravity


Activity 77A.10

Please watch this video on torque and the center of gravity:






From this video it should become clear that when doing torque problems you can "pretend" the entire weight of an object is located at it's center of mass.

Pick up a paper copy of torque problem set number #3.  When you are done check your answers here.  


Activity 77A.20

Pick up a paper copy of Catwalk and solve.