Day 53: Bike Wheel Direct Measurement Video

Day 53: Bike Wheel Direct Measurement Video

AP Physics C: I had to leave early today, so AP Physics students practiced their rotational motion problem solving using this direct measurement video. Click picture above to view video (QuickTime).

Here’s the lab handout. (It is focused on rotational kinematics and energy because we haven’t done torque and Newton’s Second Law for Rotation yet.): LAB DMV Bike Wheel Energy 2015 (word)

NGSS Science and Engineering Practices:
#4. Analyzing and interpreting data
#5. Using mathematics and computational thinking

Day 53: Bike Wheel Direct Measurement Video

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Day 65: Constant Current Source Circuit Activity

I wanted my AP Physics 2 students to review the behavior of resistors in series and in parallel but from a new perspective. Inspired by the article “Experimenting with constant current and voltage sources” in The Physics Teacher, I provided students with solar panels instead of batteries and had them investigate how the voltage across and the current through the source changes when a second resistor is added in series or in parallel. I told them upfront that the solar cells were constant current devices. I should have left that unsaid and let them come to that conclusion on their own. Regardless, I hope that this introduction to solar cells will provide a hook when discussing the photoelectric effect next semester in our quantum unit.

Day 65: Constant Current Source Circuit Activity

The solar panels only function as constant current sources for a range of voltages and resistive loads. I need to investigate the best combination of light intensity and resistors to improve the outcome of this lab. Those groups investigating the effect of adding a resistor in parallel had good results, but the groups investigating the effect of adding a resistor in series did not.

  ##circuits ##setbacks ##paradigmlab  

Day 64: Circuits Peer Instruction

Even after a previous physics course with a fantastic focus on conceptual understanding of circuits, my AP Physics 2 students still struggle when reasoning through some scenarios. Today, I posed the following question:

Day 64: Circuits Peer Instruction

Students agreed that bulb A would again be brighter. They were also able to justify their answer by stating that the current through the bulbs is the same and the resistance of the bulbs is different. What threw them was when I asked which bulb had the greater resistance.

  ##circuits ##peerinstruction  

Day 52: Balanced Forces in Motion

College-Prep Physics: We’ve been looking solely at forces in static cases. Now it’s time to look at moving cases. So I asked students to complete the following chart on a whiteboard:

Day 52: Balanced Forces in Motion

What’s true about the forces in the constant speed cases? In the speeding up and slowing down cases?

Then I tried to address the misconception/difficulties kids have with constant speed = balanced forces (wouldn’t it just not move?) by demo’ing dueling fan carts. First with fan carts off, then with both on — what happens after I push?

Day 52: Balanced Forces in Motion

NGSS Science and Engineering Practices:
#2. Developing and using models

Day 52: Balanced Forces in Motion

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Day 51: Rotational Kinetic Energy

AP Physics C: Today we derived the formula for rotational kinetic energy and showed that the total kinetic energy is simply the sum of the transnational and rotational energies. We teased out the relationships by analyzing the following 3 problems.

#1 Because we haven’t seen the rotational kinetic energy formula yet, they had to determine the linear speed of each sphere first for this problem:

Day 51: Rotational Kinetic Energy

#2. This one is easy.

Day 51: Rotational Kinetic Energy

#3. For this one, they had to figure out the net velocity of each sphere.  The orange ones were easy. The blue ones were trickier (2D vectors!).

Day 51: Rotational Kinetic Energy

And low and behold … all that crazy work to work out #3 turned out to yield the sum of #1 and #2!

NGSS Science and Engineering Practices
#5. Using mathematics and computational thinking

Day 51: Rotational Kinetic Energy

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