• Question: How can a person ride a motorcycle 100 mph but not stand up in a 100 mph wind ?

    Asked by Sarah N x to Ashley, Catherine, John G, Laura, Ray on 12 Nov 2014.
    • Photo: Laura Tobin

      Laura Tobin answered on 12 Nov 2014:

      Good question! I never thought of that. It has to do with Newton’s 2nd Law of motion F = m * a (Force = mass * acceleration). This means that the force on an object is equal to the mass m of that object multiplied by the acceleration.

      If you stand in the wind, the only force acting on you (other than gravity) is the wind pushing you, so you fall over. If you try to walk, the 100 mph wind is too strong and you fall over. Your force is not strong enough to compete against the force of the wind.

      Now if you are on a motorbike, you have an extra force from the engine of the motorbike. This is powerful enough to help propel you forward. However if it’s a windy day, the force of the wind will push you back and the motorbike will wobble.

      This is the same reason why rockets burn up large quantities of rocket fuel to help push them away from the force of gravity and up into the air.

    • Photo: John Ging

      John Ging answered on 12 Nov 2014:

      You’re not comparing like with like!
      Try standing on a motorbike at 100mph. I’ll bet you cant do that either.

      It’s basically down to the forces in play. As Laura said, standing still only has one other downward force (gravity) but there’s also friction and others at play. On the bike, you’ll have lots of other forces and acceleration. It also depends on external factors such as environment. Things like buildings and trees cause turbulence as wind moves around them which causes instability. A 100mph wind may not be direct whereas at 100mph, the force is usually coming from in front of you. You can stand in 100mph wind if its focussed straight at you in a wind tunnel!

    • Photo: Ray Alcorn

      Ray Alcorn answered on 12 Nov 2014:

      I have been on a bike at 100mph and I have felt the forces. I also understand the aerodynamics behind this but it is tricky to get across in a short answer. Basically on a bike you are a not standing up and b not getting the same force due to the subsonic pressure wave created by the bike and it’s screen in front of you and the fact that the bike designers have ensured that the rider sits in this pressure bubble behind the bike.

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