Potential+and+Kinetic+energy

Potential and Kinetic Energy Notes



Kinetic energy Eureka! media type="file" key="Eureka! Episode 9 - Kinetic Energy.mp4" width="300" height="300"

Potential energy Eureka! media type="file" key="Eureka! Episode 10 - Potential Energy.mp4" width="300" height="300"

Let's say you have two steel balls moving frictionless on a plane, they have the same mass (m) but different speeds: v and 2v, and you want to stop them with the same force F.
 * For those of you interested in the exponent of 2 in the kinetic energy formula.....**

If you need a time (t) for the one with speed v, then you need a time 2t to stop the one with speed 2v, because V = a*t and a is the same: a = F/m.

Now, why the work you make on the second ball is not 2 times the work you make on the first, but it's 4 times instead?

Work is F*S where S is the space covered. In a constant accelerated motion, S = (1/2)*a*t2 so if time doubles, space becomes 4 times.

So, F is the same but S is 4 times and for this reason the work you have to make to stop the second ball is 4 times the one required for the first.


 * The work for slide 3 - skateboard problem! Answer with #3 given a height of 3 m .... CHALLENGE (or HW if you did not try last nights HW) try to find all of the values if no height is given, only the fact: the skateboarder is at his maximum height!**

Phet physics - energy skatepark lab (blank copy)

Phet physics - energy skate park activity and practice problem answers

PE / KE information and practice problems (blank copy)

Answers to PE/KE practice problems

Energy song media type="custom" key="24298108"

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Practice Problems (answers listed at the bottom)

Additional practice problems (blank)

Additional practice problem (answers)


 * 21 PRACTICE PROBLEMS FOR CREDIT (ANSWERS):**

Lab question - answers: