The Perpetual Motion Club by Sue Lange Read Free Book Online

Davidson paused to clear his throat. “There is a pull of gravity in the opposite direction of each lead weight. Added all together, they pull in both directions equally on each thing . . . ”
    “Lead weight. Terrific answer. Great answer. Wonderful answer.” Mr. Brown turned to the crowd. “And wrong, of course.”
    The class laughed. Elsa rolled her eyes.
    Mr. Brown signaled everyone to quiet down. “Gravity does pull against the weights as they rise, but there’s more lead weight on the right side as Ms. Newman so ingeniously pointed out. The wheel is constantly overbalanced. It should move to the right. And in fact . . . ” He gave the wheel a slow turn. “ . . . as you can see by turning it slowly, there’s actually more weight on the side pulling it in the opposite direction. But that weight is there only for a moment and what really happens . . . ”
    He continued turning until the lead weight at the top of the wheel suddenly jerked forward to the right as its arm unfolded.
    “ . . . is that the position of the top weight changes drastically and forcefully. It swings out away from the center of rotation. Why isn’t this minute amount of forward acceleration enough to keep the thing going perpetually? Mr. Sun?”
    “Torque?” Mr. Sun blinked his answer which sounded more like a faltering question.
    “Uh, torque.” Mr. Brown frowned. “Good answer but not totally right. Torque is what is giving it that bit of energy actually. Since torque increases the further you are from the axis of rotation, it gives it that little extra push when the arm extends out. This should be enough to make it perpetually move to the right, so that’s obviously not what’s stopping it. Yes!”
    He turned abruptly to the audience like a maniacal lawyer proving beyond the shadow of a doubt that Miss Scarlet couldn’t be in the conservatory with a wrench because he has the card that says she was in the laundry room. The audience nodded their heads. Mr. Sun looked at his feet. He didn’t know why torque was not totally right. He did not really know what torque was. It just sounded so right.
    Mr. Brown turned back to the row of initiates. “How about it, Ms. Danforth? If it’s not torque stopping this crazy thing, what is it?” He took a step with an outstretched hand to the lanky chestnut-headed one in the center of the line of students. Her face was hidden by hair hanging straight down in front of her face.
    The class fell silent. Ms. Danforth was painfully shy. Surely, Mr. Brown would not rank out on her. It would be too hurtful to watch.
    Elsa wished she could disappear. She hated when Brown went off on students. It was bad enough he won points at stupid kids’ expense. It was bad enough when he used Elsa as an example of what a good student was. But this badgering of someone crippled by shyness was the worst. Sure, Julie Danforth should grow up and get a grip, but Brown was not a child psychiatrist. He wasn’t even a real teacher. It wasn’t his place to force someone to be something they weren’t.
    Ms. Danforth hooked the left side of her mane behind her ear, took a deep breath, and with a hopeful questioning look on her face mumbled something.
    “What?” Mr. Brown cupped his ear in his hand and stepped to just in front of Ms. Danforth. “I didn’t hear you,” he said.
    She whispered something into his cupped hand.
    The man stepped back to regard the audience and bark: “Ms. Danforth, can you please say that louder for those of us in the cheap seats?”
    The class snickered.
    Elsa racked her brain for a way to help Julie Danforth.
    Meanwhile, Ms. Danforth, quite sure she’d made a blunder and didn’t know whether to run out of the room now or do as she was told, whispered, “Inertia?”
    “Inertia!” thundered Mr. Brown. “Inertia. Class, Ms. Danforth feels that inertia is what’s stopping the wheel? What shall we do with such an answer?”
    Regardless of their previous empathy toward Ms. Danforth, they