Placeholder Image

字幕表 動画を再生する

  • In 1959, something happened that revolutionized

  • NASCAR's stock-car racing:

  • the introduction of Daytona International Speedway.

  • Daytona was unlike any race track

  • before it because of these:

  • banked turns.

  • Turns had towering walls that sloped

  • downwards to the center.

  • Walls that NASCAR's stock cars would drive onto.

  • Daytona's banks were a whopping 31 degrees,

  • significantly steeper than the relatively flat

  • 12-degree banks at Martinsville or Occoneechee Speedways.

  • In the first year of Daytona, stock-car drivers qualified

  • at speeds of more than 140 mph.

  • And today, at the same track, that speed is

  • more like 200 mph,

  • in large part because of the steep banks.

  • Which raises the question:

  • How do banked walls help cars go faster?

  • Detractors of NASCAR joke that, to finish a race,

  • all you have to do is turn left.

  • To NASCAR fans' chagrin, it's somewhat true.

  • For the majority of NASCAR races,

  • most of the lap is completed while turning, or cornering.

  • What critics misunderstand is that it's the turns

  • where good drivers earn their keep.

  • Viewers will see stock cars rocket past

  • each other in the straightaways and think,

  • "Well, the faster car had more horsepower."

  • Not so true.

  • The speed that the driver uses to pass

  • comes largely from the momentum they collect

  • in the curve they just left.

  • The winningest NASCAR drivers, then, are the ones

  • that understand the corners the best,

  • change direction the fastest, pick the best lines,

  • and apply power at the right times to navigate

  • the corners better than their competitors.

  • It's the corners where the races are won.

  • Going straight is easy.

  • Newton's law of inertia tells us

  • that an object going straight will keep going

  • straight until something makes it change direction.

  • So driving a stock car on a straightaway,

  • even at 180 mph, would be fairly easy for you or me.

  • It's turning that presents some challenges.

  • To turn, a force needs to push the car sideways.

  • That force is centripetal force.

  • Imagine a ball attached to a string.

  • When I twirl the ball in a horizontal circle,

  • the tension in the string provides

  • the centripetal force to make the ball curve.

  • Our stock cars don't have strings attached to them.

  • The centripetal force needed to move the car left is caused

  • instead by friction at the tires.

  • But at high speed, the force of friction at the tires

  • alone is not enough to pull the car to the left.

  • Let me explain by example.

  • Think about turning sharp circles in a flat parking lot.

  • The faster you go, the more unsteady the car will be.

  • With enough speed, the car will slide out.

  • Taking the first turn at Bristol Motor Speedway

  • at 130 mph requires an immense

  • 16,000 pounds of force

  • to move the car to the left.

  • That's where high banks come in handy.

  • When an object presses onto a surface,

  • the object feels an equal force in the opposite direction.

  • So for a stock car on a flat track, the track will push up

  • with a force equivalent to the weight of the car.

  • On a banked track, however, only part of the force

  • from the track goes straight up.

  • The angle of the track directs the rest

  • of the force towards the center.

  • And that's exactly the direction

  • the driver is trying to turn.

  • The extra force from the banked track,

  • combined with friction from the tires,

  • is enough to turn the car safely.

  • So the steep, banked turns let drivers maintain

  • greater speeds into and through the turns.

  • NASCAR's banks are for cars going at race speeds.

  • At lower speeds, the 33-degree bank

  • at Talladega Superspeedway would be enough to slide

  • a car down to the bottom of the track.

  • In fact, if you or I wanted to take a lap

  • around Talladega in, say, a street car,

  • we'd constantly be turning right

  • just to stay up on the wall.

  • But you don't need to be a stock-car driver

  • to test a banked turn for yourself.

  • Banked turns exist on our roads, too,

  • on freeway on-ramps and interchanges.

  • For heavy vehicles, like trucks and buses,

  • friction alone may not provide enough force to turn safely,

  • especially if the driver doesn't slow down enough.

  • A slightly banked turn, with a gentle grade of, say,

  • 15 degrees or less, can help push

  • the vehicle into the turn.

  • So, for NASCAR, banked turns simultaneously

  • create lateral force that, in addition to friction force

  • at the tires, create enough centripetal force

  • in total to get stock cars moving to the left,

  • but also enable them to travel at higher speeds

  • without sliding or flying off the track.

In 1959, something happened that revolutionized

字幕と単語

ワンタップで英和辞典検索 単語をクリックすると、意味が表示されます

B1 中級

The One Design Change That Made NASCAR Races Faster

  • 1 1
    joey joey に公開 2021 年 05 月 25 日
動画の中の単語