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:

2015 APC Energy Principle

#2. This one is easy.

2015 APC Energy Principle (1)

#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!).

2015 APC Energy Principle (2)

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


About Frank Noschese

HS Physics Teacher constantly questioning my teaching.

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