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AGC/United Learning • 1560 Sherman Ave., Suite 100 • Evanston, IL 60201 • 800-323-9084

COLLEEN: BUT WHAT ABOUT ALL THAT OTHER ENERGY THAT DOESN’T GET ANY USEFUL WORK DONE? DARREN: SOMETIMES WE PUT ENERGY INTO A SYSTEM, BUT IT DOESN’T DO THE WORK WE HAD IN MIND. RIGHT NOW, I’M USING THE ENERGY STORED IN GASOLINE, BUT I’M NOT GO- ING ANYWHERE. WE CALL THIS EXTRA INPUT “WASTE EN- ERGY.” COLLEEN: WHEN I SLIP OR KICK UP SNOW WITH A POOR STRIDE, I WASTE ENERGY. THAT’S STILL WORK, BUT IT’S NOT HOW I WANTED TO USE MY ENERGY, SO IT ISN’T USEFUL WORK. CRAIG BULAWKA: BRYCE, ONE OF THE MOST COMMON ER- RORS SKIERS MAKE IS POOR WEIGHT SHIFT, WHICH RESULTS IN POOR BALANCE AND AN INEFFICIENT ENERGY TRANSFER. COLLEEN: I USE A LOT OF ENERGY OVERCOMING FRICTION; THE FRICTION OF SNOW, THE FRICTION IN MY CLOTHING, AND THE FRICTION AGAINST THE AIR. I’M DOING WORK, BUT IT’S NOT USEFUL WORK. SO THE ENERGY IS WASTED. CRAIG BULAWKA: YOU COULD WASTE A LOT OF ENERGY IF YOU DON’T PAY ATTENTION TO YOUR SKI BASE. BRYCE: YEAH. CRAIG BULAWKA: WHEN YOU GLIDE, YOU ACTUALLY RIDE ON A CUSHION OF WATER.WE USE GLIDE WAX ON THE TIPS AND THE TAILS TO REDUCE THE FRICTION BETWEEN THE SKI BASE AND THE SNOW. SO, OF COURSE, AN UNEVEN SKI BASE CAN CAUSE A LOT OF UNNECESSARY FRICTION, AND YOU CAN WASTE A LOT OF ENERGY THERE. DARREN: CROSS-COUNTRY SKI CLOTHING IS DESIGNED TO MAKE MOVEMENT EASIER, AND REDUCE FRICTION WITH THE AIR. LESS FRICTION, LESS WASTE ENERGY. SO ACCORDING TO THE “FIRST LAW OF THERMODYNAMICS”: ENERGY CANNOT BE CREATED OR DESTROYED, ONLY CONVERTED FROM ONE FORM TO ANOTHER. AND WHEN WE DO WORK, WE TRANS- FER ENERGY FROM ONE SYSTEM TO ANOTHER. IF THE INPUT ENERGY PERFORMS THE WORK WE WANT, WE CALL IT USEFUL ENERGY. THE REST OF THE ENERGY TRANSFORMED IS CON- SIDERED WASTE ENERGY. SARAH: INPUT ENERGY MAKES THE MOTOR RUN. SOME IN- PUT ENERGY BECOMES WASTE ENERGY. AND SOME IS USEFUL.

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