If you missed class today:
Problems 1-3 were assigned on the Unit 5 hmwk sheet (note you can find that sheet on yesterday's page.
I twirled a ball over my head, parallel to the floor, and the classes answered the questions concerning the direction of the velocity, acceleration, and force involved in circlular motion. (Note: Big Picture below...)
At least 13 students figured out the 3rd day of Physmas compared to only six figured out the 2nd day of Physmas yesterday.
We went outside and collected the times with stopwatches, in groups of two (the same lab partners as the Bull's Eye Lab), for a 1 meter, 2 meter, 3 meter, and 4 meter radii twirls of a fresh egg in a can. Four students each volunteered do twirl one of the radii 10 times outside as lab groups timed the twirls.
Below are the videos for each period. If you were gone, watch each video and time up to 10 revolutions for each radii (if you cannot get 10 revolutions you may time fewer) and then go to yesterday's webpage and download 1st periods example of g's on an egg where we did a 0.5 m radius in class.
I twirled a ball over my head, parallel to the floor, and the classes answered the questions concerning the direction of the velocity, acceleration, and force involved in circlular motion. (Note: Big Picture below...)
At least 13 students figured out the 3rd day of Physmas compared to only six figured out the 2nd day of Physmas yesterday.
We went outside and collected the times with stopwatches, in groups of two (the same lab partners as the Bull's Eye Lab), for a 1 meter, 2 meter, 3 meter, and 4 meter radii twirls of a fresh egg in a can. Four students each volunteered do twirl one of the radii 10 times outside as lab groups timed the twirls.
Below are the videos for each period. If you were gone, watch each video and time up to 10 revolutions for each radii (if you cannot get 10 revolutions you may time fewer) and then go to yesterday's webpage and download 1st periods example of g's on an egg where we did a 0.5 m radius in class.
Since in 2013 today was much colder, look at yesterday when we did all the g on an egg videos.
2012 videos here and below Period 1
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Period 5
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Period 7
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8th Period g's on an egg Note:either get as many revolutions as you can (like 3 instead of 10) or watch another periods....the camera was acting up for the 2 m and 3 m videos
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The Big Pictures:
1. In circular motion the velocity is still distance divided by time but now the distance is the circumference of the circle and the time has a special name called the period so the magnitude of the velocity is 2*PI*r/T
2. We timed 10 revolutions and then divided that time by 10 so to get a better average time for one revolution.
3. The direction of the velocity is tangent to the circle at any instant as if you let go or the string broke the object would fly off tangent to the circle at the point.
4. The acceleration is v^2/r (we'll cover why later) but we can feel we are constantly pulling in on the object so since the force is inward, the acceleration direction is inward since F = m a.
5. To calculate the g's on the egg is experiencing we just needed to divide the acceleration we obtained by 9.8 m/s^2 as g's is just how many multiples of Earth's gravity an acceleration is. .. Note g's is unit less thus g's IS NOT A FORCE as force is in Newton units...
6. Our egg survived all the g's as our g's stayed under a dozen maximum and the shape of an egg allows over 20 g's. That is why engineers use the egg shape for building strong structures and is why eggs are placed in an egg carton standing up and NOT laying on their side (as sideways an egg is real weak).
2. We timed 10 revolutions and then divided that time by 10 so to get a better average time for one revolution.
3. The direction of the velocity is tangent to the circle at any instant as if you let go or the string broke the object would fly off tangent to the circle at the point.
4. The acceleration is v^2/r (we'll cover why later) but we can feel we are constantly pulling in on the object so since the force is inward, the acceleration direction is inward since F = m a.
5. To calculate the g's on the egg is experiencing we just needed to divide the acceleration we obtained by 9.8 m/s^2 as g's is just how many multiples of Earth's gravity an acceleration is. .. Note g's is unit less thus g's IS NOT A FORCE as force is in Newton units...
6. Our egg survived all the g's as our g's stayed under a dozen maximum and the shape of an egg allows over 20 g's. That is why engineers use the egg shape for building strong structures and is why eggs are placed in an egg carton standing up and NOT laying on their side (as sideways an egg is real weak).