On a train speeding through the French countryside, we find our intrepid feline travelers, Henri and Cassie, sitting in their private compartment. Henri is lying on her seat contently reading a book while Cassie stares glumly out the window.

“I’m bored,” complained the little kitten. “Why can’t I play with my ball?”

Looking up from her book, Henri gives Cassie a long look. “Because I doubt the other passengers would appreciate you running up and down the train making a racket.”

“I’d be quiet,” pleaded Cassie.

“”I’m sorry, but the answer is still no,” replied Henri firmly. “Why don’t you read or take a nap. It’s only another two hours until we reach Amsterdam.”

“It’s not fair,” grumbled Cassie, turning back to the window. “I never get to do what I want.”

Henri went back to her book, but couldn’t concentrate. She kept glancing at the kitten sadly staring out the window. At last, she closed the book and sat up. “I did promise to tell you another Dynamics Cat story.”

Cassie’s eyes brightened. “Really?”

“Yes, really,” answered Henri, patting the seat beside her.

Cassie jumped over and curled up next to her.

“Well,” began Henri in a hushed tone, “it all started when Dynamics Cat was flying home after helping NASA correct the orbit of a wayward satellite …”

High in the upper atmosphere, Dynamics Cat, that champion of force and acceleration, is flying homeward when his super hearing detects a weak cry for help.

He recognizes the voice immediately. “That’s Billy Harper’s voice,” he cries, heading towards the source of the sound.

Landing in the playground of Newtonville Middle School, he finds that the usual commotion of recess has been replaced by the eerie sight of all the students and teachers lying on the ground. Weak cries of, “help us Dynamics Cat,” can be heard. Spying Billy Harper lying nearby, he rushes over to him.

“What happened here, Billy?”

“It was Mr. Inertia,” he gasps. Struggling, he lifts his hand to point, “over there.”

Looking up, Dynamics Cat sees his enemy resting on a bench near the playground.

“I’ll take care of this,” assures our hero as he gets up and strides boldly towards Mr. Inertia.

“This ends now,” he hisses, stopping in front of him.

For a moment, Mr. Inertia just sits there, but finally his eyes fall on the cat before him. In a casual voice he responds, “oh hey, Dynamics Cat. I was wondering when you’d get here.”

“Now that I’m here,” rejoins Dynamics Cat leaping onto the bench. “it’s time for you to leave.”

“Actually, I kind of like it here,” replies Mr. Inertia casually.

“Sadly, you have no choice,” counters Dynamics Cat preparing to lift him.

“I don’t,” replied Mr. Inertia sounding confused. From his pocket he pulls out a small box, pressing a button on it. As he does so, what appears to be a small satellite dish rises from a box near the center of the playground. “This is my Inertializer,” he says cheerfully. “With it I will turn the Earth into a wonderful place of immobile tranquility.” He glances at Dynamics Cat, “starting with you.”

Like a shot, Dynamics Cat takes off towards the Inertializer, but merely bounces off when colliding with it.

Mr. Inertia chuckles. “Did I forget to mention that it has special inertia shielding not even you can penetrate?” He presses another button and the dish swivels towards our hero. “Say goodbye to moving.”

Dynamics Cat leaps into the sky, but not quite fast enough as the red beam from the Inertializer hits his tail. Immediately, he feels his strength waning and his speed dropping. Any second now, I’ll be plummeting like a rock, he thinks looking at the ground below. Seeing the Inertializer gives him an idea. “If only I can get in position.”

Using his remaining strength, our hero reaches a point nearly a thousand feet above the Inertializer and then, unable to go on, falls. Groans come from those trapped in the playground as Dynamics Cat tumbles helplessly Earthward. With a loud crash, he lands on the Inertializer, crushing it. For a long moment he lies there unmoving, but suddenly leaps into the air landing beside Mr. Inertia.

“But how?” cries the confused villain. “There’s no way you could have gotten through the inertia shielding. Well at least none I can think of.”

“That’s because you forgot one thing, Mr. Inertia,” explains Dynamics Cat. “By increasing my inertia, you also increased the amount of kinetic energy I generated while falling. It was enough to destroy your machine and free me from its effects.”

Mr. Inertia scratches his head. “So you fell faster because my machine increased your inertia?”

Dynamics Cat shook his head. “Since gravity acts as an acceleration, everything, regardless of mass, falls at the same speed. Kinetic energy is one half mass times the velocity squared. By increasing my inertia you made my mass greater, causing a higher kinetic energy when I hit your machine. Essentially, I used your own inertia against you.”

Mr. Inertia nods. “I understand now. Well I certainly won’t make that mistake again.”

Dynamics Cat smiles. “Well as much as I enjoyed our dynamics lesson, it’s time for you to go.”

“I really like it here,” protests Mr. Inertia while twisting the knob of a device on his belt. “Plus, using my personal inertializer, I’ve increased my own inertia so that even with your great strength, you’ll be unable to move me.”

“Considering your lackluster knowledge of dynamics, I doubt that,” retorts Dynamics Cat. However, taking hold of his nemesis, our hero is shocked to discover that Mr. Inertia is right.

Mr. Inertia seems surprised as well. “Wow,” he exclaims, “it really works.”

Releasing Mr. Inertia, Dynamics Cat looks at the students and teachers lying on the ground. “I’ll find a way,” he promises before reluctantly flying away. As he does, he tries to block out the muffled cries of “don’t leave us Dynamics Cat.”

Mr. Inertia surveys the playground and smiles. “Gee, this feels really good. I’ve never won anything before.”

“Dynamics Cat would never leave us,” calls out Billy Harper in as loud a voice as he can muster.

Mr. Inertia merely shrugs, “Maybe, but I still won.”

“I wouldn’t be so sure about that, Mr. Inertia.”

Mr. Inertia looks up in surprise to see Dynamics Cat standing four feet in front of him.

“But I still won, right?” he asks our hero.

Ignoring him, Dynamics Cat continues, “I may not be able to move you, but I know something that can.” In a single motion, he pounds the ground in front of him with a mighty paw. Immediately, the ground begins to crumble. Mr. Inertia looks around in disbelief as Dynamics Cat whispers, “gravity.”

As the ground around the bench falls away, Dynamics Cat smiles. “You know what they say Mr. Inertia: what can’t go up will certainly go down.”

With a cry of “but I really wanted to finally win,” Mr. Inertia and the bench disappear into a gaping void.

Turning around, Dynamics Cat sees the students and teachers getting up as Mr. Inertia’s influence fades away. Billy Harper rushes up to Dynamics Cat and peers over the edge of the hole. Unable to see the bottom, he asks, “how deep is it?”

“About a mile.”

“Wow, you did that with a single punch?” marvels Billy.

Our hero gives a slight chuckle. “Not at all. While I was gone, I tunneled under Mr. Inertia leaving just enough ground to support him. While his device could prevent me from lifting him, it was no defense against gravity.”

“So is that the end of Mr. Inertia?” asks a wide-eyed Billy.

“No Billy, just as the power of dynamics protects me, he is protected by the power of inertia. He’ll be back, but hopefully not for a long time.”

The school bell rang, signaling the students to return to class. “Really wasn’t much of a recess,” observed Billy looking at Dynamics Cat. “Do you think you could ask the principal if we could have another one?”

Shaking his head, Dynamics Cat slowly rises into the air and answers, “sorry Billy, but some things are beyond even my abilities.”

Henri leaned back and stretched. “Did you enjoy the story?”

“Yes,” cried Cassie excitedly. “It looked like Mr. Inertia was going to win, but Dynamics Cat was too smart for him.”

“Yes he was,” agreed Henri.

“What was that kinetic energy thing Dynamics Cat mentioned?” wondered Cassie.

Henri smiled, glad to see Cassie interested in learning. “Kinetic energy is the energy an object has when it’s moving.”

Cassie gave her a blank look.

Picking up her book, Henri said, “I’ll show you. Look what happens when I drop my book.” She let go and her book fell to the floor. “You see, gravity pulled the book to the floor and as it fell the book gained kinetic energy and then when it landed: splat.”

“So that’s how Dynamics Cat destroyed the Inertializer?”

“Exactly.”

They were interrupted by the shrill sound of a train whistle.

“Looks like we’re nearing Amsterdam,” announced Henri. “We’d better get our stuff together.”

Cassie gave Henri a quick hug. “Thanks for the story. It made the trip go much faster.”

“I’m glad you enjoyed it,” answered Henri, whiskers turning up as she smiled. “I sure we’ll find time for some more as we continue our travels.”