## Kinetic Energy NGSS MS PS3-1 and MS PS3-5

In the Kinetic Energy mini unit, students use marbles, ramps and blocks to learn how mass and speed affect an object’s kinetic energy. They play with the Energy Skate Park PhET simulation to construct and analyze graphs of mass, speed and kinetic energy. Finally, students use a double ball bounce (drop a tennis ball on top of a basketball) to construct an argument in support of the claim: When the kinetic energy of an object changes, energy is transferred to or from the object.

Extension activities challenge kids to create a roller coaster for a marble and calculate the energy of the ride!

Anchor Phenomenon Ideas: To hook students immediately, demonstrate the double ball drop (drop a tennis ball with a ping pong ball on top) and let the discussion begin! Kids will come back to this phenomenon for their summative assessment as they build a deeper understanding of energy.

Make it Relevant: Focus on the fun! Kinetic energy is everywhere. Point out examples of kinetic energy as kids walk, play sports and listen to music.

Tips and Tricks: Set out meter sticks, cardboard or wood to use as ramps, textbooks, different sizes of marbles and blocks or dice and let kids play. Allow them to build and explore before directing them back to the guided investigations of questions two and three. Remind students to make sure they are changing only one variable at a time as they collect data.

Students continue to gather data as they explore the University of Colorado PhET Energy Skate Park in question four. This engaging simulation allows students to determine how speed and mass affect the skater's kinetic energy.

Student work sample of question two

Share the formula for kinetic energy with students:

KE = ½ (mass in kg)(velocity in m/s)2

Discuss with students why this formula makes sense: As mass and/or velocity increase, so too does the product. Then, ask students which factor (mass or velocity) has a greater impact on an object’s total KE. Explain that since velocity is squared, increases in velocity will have an exponentially greater effect on total KE. You can also share with students that energy is measured in Joules (kgm2/s2).

The double ball drop in the summative assessment shows that when the kinetic energy of an object changes, energy is transferred to or from the object. As you drop the basketball with the tennis ball on top, both balls gain kinetic energy. Right before the basketball hits the ground, it has maximum KE. Some of this energy is changed into elastic potential energy as the basketball deforms and bounces. This potential energy is then transferred to the tennis ball, allowing it to bounce higher than its original drop height.

This video of the stacked ball drop from the Physics Girl explains the physics behind this phenomena and how it is related to a supernova!

Extension Activity: The foam tubes used to insulate pipes work well to build marble roller coasters as long as kids don't bend them in half (they do break). Ramps made of paper also work. Masking tape can secure the tubes to any available wall, window or door.

As students calculate the marble's PE and KE, remind them to use kilograms as the unit for mass and meters as the unit for height. For the most accurate KE reading, encourage students to find the speed of the marble over the first long section of their track.