Thrills and spills: you don't have to jump out of a plane to live on the edge this summer. Thanks to physics, you can head to the amusement park for spine-tingling terror--without the danger. (Physics: Newton's first law/inertia).ARE STOMACH-FLIPPING roller-coaster loops your idea of fun? Then here's a question you probably don't want to ask yourself mid-loop: If gravity causes objects to fall toward Earth, why doesn't your coaster train plunge to the ground? The answer begins with Newton's first law of motion Noun 1. Newton's first law of motion - a body remains at rest or in motion with a constant velocity unless acted upon by an external force first law of motion, Newton's first law , or the law of inertia law of inertia See under Newton's laws of motion. , which states that moving objects keep moving in a straight line unless acted on by an outside force. The outside force in this case? To find out, take a closer look at the physics of looping. "Vertical looping is all about inertia and acceleration," explains Jeff Pike, a design engineer at Great Coasters International in Sunbury, Penn. Inertia is the tendency of a body--a roller-coaster train, for example--to resist a change in motion. "Once the train enters the vertical loop, the train wants to keep going straight," says Pike. "But the track gets in the way." Its upward curve interferes with the train's inertia. So, according to according to prep. 1. As stated or indicated by; on the authority of: according to historians. 2. In keeping with: according to instructions. 3. Newton's first law Noun 1. Newton's first law - a body remains at rest or in motion with a constant velocity unless acted upon by an external force first law of motion, Newton's first law of motion , the track is the outside force that makes the train change direction and speed--a movement called acceleration. Add a curved path and you get centripetal acceleration centripetal acceleration Property of the motion of an object traveling in a circular path. Centripetal describes the force on the object, directed toward the centre of the circle, which causes a constant change in the object's direction and thus its acceleration. : As the train speeds into the loop, it accelerates because the track forces it upward. (As the train climbs higher it also loses speed, but regains speed when it plunges down the loop's other side.) Since the train wants to keep going straight--not up--you're pushed into the track. When you're at the top of the loop, gravity wants to yank Yank steamship stoker vainly tries to climb the social ladder, then fails in attempt to avenge himself on society. [Am. Drama: O’Neill The Hairy Ape in Sobel, 339] See : Failure (jargon) yank you to the ground, but centripetal acceleration makes the train hug the track and inertia pushes you into your seat--even when you're upside down! The force your body feels is measured in g's: one g equals the force of gravity. (Standing on the ground, you feel the force of one g.) At the top of a vertical loop, the centripetal force Centripetal force The inward force required to keep a particle or an object moving in a circular path. It can be shown that a particle moving in a circular path has an acceleration toward the center of the circle along a radius. that glues you to your seat must be equal to or greater than one g to counterbalance gravity's downward tug. "As long as the centripetal acceleration is equal to the force of gravity, you can flip head over heels without crashing," Pike says. So you can save the "spills" for lunch! RELATED ARTICLE: Roller-coaster physics. 1 Gravity pulls the train down. 2 Top of loop: Inertia presses the train into the track and counterbalances gravity. 3 Centripetal force whips you to the seat's outer edge. The banked track forces the train to change direction. [ILLUSTRATION OMITTED] |
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