Sunday, February 16, 2020
Scientists discover an Archaea organism that could be related to first multicelluar life
Archaea is that weird, fascinating domain of primitive single cell organisms that can live in the toughest possible environments, where we used to think life was impossible. Extreme heat, extreme cold, no oxygen, living on sulfur, extreme pressures, high levels of radiation, and so on. Some new samples of ocean dirt taken from 2500 meters down near Japan produced a discovery of an organism that has the genetics related to some of the earliest single celled organisms on earth...similar to ancient bacteria, these hint to the first life some 2 billion years ago. And these archaea could be the link between single cell life and the first multi-cell life. That is still a mystery and is not well understood. Just a few years ago a similar archaea was found that has some sections of genetics related to the earliest known 'complex' life forms.
Thursday, February 13, 2020
Review stuff
To be prepped for a quizzam, there is a review set for gravity in the Gravity folder on our 3 Chem/Phys website. Give the multiple choice and two free response problems a try, and there is a solutions file to check yourselves right away. Note that the second free response problem has to do with an elliptical orbit. The big thing there is that energy is conserved, and the total energy in an elliptical orbit is
E = -GMm/2a, where a is the semimajor axis...for the picture that is given, 2a = r1 + r2. Then use energy conservation for the first couple parts. Don't worry about the questions about angular momentum (parts d,e,f), we have not done that yet.
Additional practice problems dealing with the very basic definitions for rotational motion from Tuesday, that being with constant angular acceleration, are Chapter 9 #1, 2, 7, 13, 14, which are in the rotations packet.
Keep in mind there are videos on all the gravity topics as well as one introducing the main rotational quantities. The links to videos are on the blog. There are numerous examples in the book.
E = -GMm/2a, where a is the semimajor axis...for the picture that is given, 2a = r1 + r2. Then use energy conservation for the first couple parts. Don't worry about the questions about angular momentum (parts d,e,f), we have not done that yet.
Additional practice problems dealing with the very basic definitions for rotational motion from Tuesday, that being with constant angular acceleration, are Chapter 9 #1, 2, 7, 13, 14, which are in the rotations packet.
Keep in mind there are videos on all the gravity topics as well as one introducing the main rotational quantities. The links to videos are on the blog. There are numerous examples in the book.
Wednesday, February 12, 2020
Finding Torques - an example
Please check out an example video for finding torques, using torque = Frsin(B), where B is the angle between the force and the radius line coming from the axis of rotation. The example is for equilibrium situations.
Try practice problems Ch. 10 #1, 2, and 13, on page 7 of the rotations packet from yesterday. For constant angular acceleration and the new kinematics equations, try Ch 9 #9, 11 on page 5.
The axis of rotation will be THE reference point we use to figure out torques, angular momentum, and something called the moment of inertia, which we will worry about next time you're in.
Take advantage of the time today to try the practice rotation problems, and to help each other go over some of the gravity problems. We will have review and additional practice tomorrow, of course, to get set for Friday.
Try practice problems Ch. 10 #1, 2, and 13, on page 7 of the rotations packet from yesterday. For constant angular acceleration and the new kinematics equations, try Ch 9 #9, 11 on page 5.
The axis of rotation will be THE reference point we use to figure out torques, angular momentum, and something called the moment of inertia, which we will worry about next time you're in.
Take advantage of the time today to try the practice rotation problems, and to help each other go over some of the gravity problems. We will have review and additional practice tomorrow, of course, to get set for Friday.
Thursday, February 6, 2020
Gravity links for classes
Especially for Periods 8-9, for Thursday when Doc V will be out with a dental appointment, check out the beginnings of what we call FLUX, and the reason why gravity for most objects turns out to be an inverse-square law, or 1/r^2. The rule that is used to define and calculate this flux quantity is something we will call Gauss's law.
Notice I say "most objects." The 1/r^2 rule turns out to be true for objects that can be treated as a point mass or are spherical, like planets and stars. However, the law for gravity would actually change if the shape changes! We will think about what gravity would look like for us if the earth was a large cylinder, as well as what gravity would look like if the earth was actually flat! Gravity would behave differently! Take notes on this first video.
A second video to check out is for a hypothetical that is fun to think about - how does gravity behave inside the earth?!!?
After checking out these videos, you can work on a few things. If you need to still go through your last quizzam on momentum, check out the solutions in the Momentum folder on Doc V's school site, on the 3 Chem/Phys page. Or you can get together with your lab group to work on the pendulum lab, which will be shared with Doc V by next Wednesday. Or you can work on the conceptual questions about gravity on pages 5-6 of our packet. Note that there is a video on Einstein's principle of equivalence, if you want to check it out for the first question. This is a simple idea that led Einstein to develop his General Theory of Relativity (i.e. our modern theory of gravity).
Notice I say "most objects." The 1/r^2 rule turns out to be true for objects that can be treated as a point mass or are spherical, like planets and stars. However, the law for gravity would actually change if the shape changes! We will think about what gravity would look like for us if the earth was a large cylinder, as well as what gravity would look like if the earth was actually flat! Gravity would behave differently! Take notes on this first video.
A second video to check out is for a hypothetical that is fun to think about - how does gravity behave inside the earth?!!?
After checking out these videos, you can work on a few things. If you need to still go through your last quizzam on momentum, check out the solutions in the Momentum folder on Doc V's school site, on the 3 Chem/Phys page. Or you can get together with your lab group to work on the pendulum lab, which will be shared with Doc V by next Wednesday. Or you can work on the conceptual questions about gravity on pages 5-6 of our packet. Note that there is a video on Einstein's principle of equivalence, if you want to check it out for the first question. This is a simple idea that led Einstein to develop his General Theory of Relativity (i.e. our modern theory of gravity).
Wednesday, February 5, 2020
How to add error bars on Google Sheets
For our labs where we do trials and can find standard deviations, there is a helpful video that explains how to include these 'custom' error bars on a Google Sheets plot.
Sunday, February 2, 2020
Astrophysics Research Program for High School students
Applications are now being taken for the CIERA Summer Research Program for high school students at NU. CIERA is the astrophysics group, and juniors can apply through February 16. Note that this is a summer program with a cost of $3000 for 6 weeks of classes and work on independent research. There are need-based scholarships, as well.
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