Homework Due: Read & Study 11.1 - 11.4 – Do #1-12 p. 165

1. Homework Due: Read & Study 11.1 - 11.4 – Do #1-12 p. 165 Tonight’s HW: Read & Study 11.2, Do #21, 33, 38 p. 165-167 6 points – 1 point per problem per answer, 1 point per problem for work CLOSED NOTES TESTon CH 10 & 11 Fri 4/26 B day, Mon. 4/29 A day STUDY GUIDE – Finish by end of class on 4/23 & 4/24 for +5 on test. YOU MUST DOWNLOAD AND PRINT. If you are unable to do this, you MUST let me know by FRIDAY 4/19 so that I can photocopy one for you! Do Now: Take down your energy posters. You can take them home, but if you are planning to throw them out, CHECK WITH ME FIRST! You can hang up your Space Travel projects if you would like. Take a clicker. Then, in your notes, answer the following question: Which hoop will reach the bottom of a ramp first? They are the same mass, released on the same ramp at the same time from the same height.(You should draw this in your notes –the hoops are on my desk if you want to pick them up/ look at them!)

2. Which hoop will reach the bottom of a ramp first? They are the same mass, released on the same ramp at the same time from the same height.(the hoops are on my desk if you want to pick them up/ look at them!) • Hoop 1 • Hoop 2 • Hoop 3 • Hoop 1 &2 • Hoop 2 & 3 • Hoop 1 & 3 • All 3 @ the Same time • Not sure/ not enough info The CLOSER the bulk of the mass is from the turning axis, the LESS R.I. there is!!! It is EASY to get #2to ROTATE since it DOESN’T RESIST CHANGE! 10 Countdown

3. What is different from scenario 1 to scenario 2? Which has more torque and why? • 1 because the hand is angled • 2 because the hand is perpendicular • Same torque • Not sure/ not enough info 10 Countdown

4. What is different from scenario 1 to scenario 2? Which has more torque and why? • 1 because smaller lever arm • 2 because larger lever arm • Same torque • Not sure/ not enough info 10 Countdown

5. Which of the following produces the greatest torque? • Small force, short lever arm • Large force, small lever arm • Small force, long lever arm • Large force, long lever arm. • Not sure/not enough info 10 Countdown

6. Can the same force produce different amounts of torque? • Yes • No • Not sure/not enough info If you apply the same force to different lever arms, you can get different torques! Or, if you apply the same force, but apply it at an angle vs. perpendicular! 10 Countdown

7. Can the same torque be exerted from different forces? • Yes • No • Not sure/not enough info If you apply different forces to different lever arms, you can get the same torque! 10 Countdown

8. When the CG is not over the area of support, what force produces a torque that causes toppling? • Perpendicular force • Gravity • Support force • Not sure/ not enough info 10 Countdown

9. The 3 batons below have the SAME mass, but the mass is distributed differently. The 1st baton has most of the mass close to the handle. The 2nd baton has most of the mass far from the handle. The 3rd baton has the mass evenly distributed from the handle. Which has the GREATEST rotational inertia? The farther the bulk of the mass is from the turning axis, the MORE R.I. there is!!! 10 Countdown

10. The 3 batons below have the SAME mass, but the mass is distributed differently. The 1st baton has most of the mass close to the handle. The 2nd baton has most of the mass far from the handle. The 3rd baton has the mass evenly distributed from the handle. Which is the EASIEST to balance? The farther the bulk of the mass is from the turning axis, the MORE R.I. there is!!! It WANTS to STAY balanced since it RESISTS CHANGE! 10 Countdown

11. The 3 batons below have the SAME mass, but the mass is distributed differently. The 1st baton has most of the mass close to the handle. The 2nd baton has most of the mass far from the handle. The 3rd baton has the mass evenly distributed from the handle. Which is the EASIEST to swing like a bat? The CLOSER the bulk of the mass is from the turning axis, the LESS R.I. there is!!! It is EASY to get it to ROTATE since it DOESN’T RESIST CHANGE! 10 Countdown

12. BASEBALL PLAYERS CHOKE UP ON A BAT TO….. The CLOSER the bulk of the mass is from the turning axis, the LESS R.I. there is!!! Choking Up means more mass is CLOSER to the turning point, making it EASY to get the bat swinging since it is LESS RESISTANT TO CHANGE! • INCREASE the R.I. and make it easier to get the bat swinging • DECREASE the R.I. and make it easier to get the bat swinging • Not quite sure 10 Countdown

13. Torque Formulas • Weight alone does not produce rotation—torque does. • When balanced torques act on an object, there is no change in rotation. • 2 kids can balance a see-saw even when their weights are not equal! • A pair of torques can balance each other. • Balance is achieved if the torque that tends to produce clockwise rotation (by the boy) equals the torque that tends to produce counterclockwise rotation (by the girl.) Torque counterclockwise = Torque clockwise (Force x Lever Arm)counterclockwise = (Force x Lever Arm )clockwise

14. 11.2Balanced Torques A pair of torques can balance each other. Balance is achieved if the torque that tends to produce clockwise rotation by the boy equals the torque that tends to produce counterclockwise rotation by the girl.

15. Calculations: • Calculate the girl’s torque: • What is the girl’s weight? (this is the Perpendicular Force) • What is the girl’s DISTANCE from the FULCRUM/TURNING POINT? (This is the Lever Arm) • Calculate the girl’s torque: *Show all work; the unit for torque is the Newton Meter ( Nm) 2. Calculate the boy’s torque: • What is the boy’s weight? (this is the Perpendicular Force) • What is the boy’s DISTANCE from the FULCRUM/TURNING POINT? (This is the Lever Arm) • Calculate the boy’s torque: *Show all work; the unit for torque is the Newton Meter ( Nm) 400 N 200 N 1.5 m 3 m 400 N x 1.5m = 600 nm 200 N x 3m = 600 nm

16. 11.2Balanced Torques do the math! What is the weight of the block hung at the 10-cm mark?

17. 11.2Balanced Torques do the math! The block of unknown weight tends to rotate the system of blocks and stick counterclockwise, and the 20-N block tends to rotate the system clockwise. The system is in balance when the two torques are equal: counterclockwise torque = clockwise torque

18. 11.2Balanced Torques First, let’s check…which force has to be larger? F x LA = F x LA … So we know our ‘mystery weight’ is less than 20 N Force x Lever arm = Force x Lever Arm Force x 40 cm = 20N x 30 cm Force x 40 cm = 600 n cm Divide both sides by 40…. Force = 15 N

19. Webquest! • Follow all directions • Check in when you need clarification or assistance • PAGE 2 #8 - FIX IT: • Try to draw what will happen next if the box on the left is 15 kgand the box on the right is 60 kg • EVERY STUDENT WILL COMPLETE A WEBQUEST to KEEP (the handout you just received) • Must be finished TODAY • Anything you do not finish will be HW so that you will be successful on the POST LAB next class! • EVERY STUDENT will then use the solutions from the Web Quest to complete an INDIVIDUAL GRADED POST LAB at the start of next class!

20. The broom balances at its CG. If you cut the broom at its CG and weighed each side, which side would weigh more? • The broom HANDLE side • The broom BRUSH SIDE • They weigh the same • Not sure/not enough info 30 Countdown