Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Need for Speed

  1. Aug 23, 2004 #1
    Hey guys, have a question for you that I cannot get passed while laying out a track idea for the October races.

    The Elements:
    RC length/weight = 16 inches/7-10 pounds
    Total Track length = 44 feet (including ramp)
    Total Ramp length/height = 20 feet/20 inches
    End of Ramp to landing zone = 18-20 feet

    The RC will round it's final turn, it is now faced with 44', where 24' are level, and the other 20' will graduate at 1" per foot to create the ramp. Can the RC clear an 18-20' distance, where it's landing is level, and how fast would it have to be going?

    If you need any more info, I will try my best to provide it, thanks again!
     
  2. jcsd
  3. Aug 23, 2004 #2

    Gokul43201

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    It will need to be going faster than 15 m/s or 35 miles/hr or 50 ft/sec at take off.

    Disclaimer : This is a rough calculation, and may be off by about 20%. But it gives you a feasibility argument. If you really need a more accurate number, it will take longer to calculate that.
     
  4. Aug 23, 2004 #3
    Thank you very much for the help. You mentioned it was a rough estimate, would it relate to the speed being slower of faster? These Nitro RC's can get to 50mph, but typically that is on the road.

    If you needed me to measure and get exact measurments I will more than happy to do so.

    Also, and I hate to ask, but is there a method you used to calculate the equation, I would love to be able to tweak other areas of the track if possible using the formula you used.
     
  5. Aug 23, 2004 #4

    Gokul43201

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    I made 2 approximations :

    1) I neglected air resistance (I don't imagine this is more than a 10% effect)
    2) I neglected the slope of the take off velocity=0.08 (this may cause a 10% -20% error too, in the opposite direction)

    I expect the two errors to nearly cancel out...but it's possible that the second is greater than the first.

    The formula (after making these approximations) is : speed, v = d* SQRT (g/2h)

    where d : dist to landing zone = 18 '
    g : accel. due to grav. = 32 ft/sec^2
    h : height of ramp = 1.67 '

    NOTE : The second approximation doesn't work if you increase the slope by much.
     
  6. Aug 23, 2004 #5
    I hate the british system of measurement. Why cant we all use the metric system. ARGHHHHHH!!!
     
  7. Aug 23, 2004 #6
    Thank you again for the help, and the method you used for this calculation.
     
  8. Aug 23, 2004 #7

    Gokul43201

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    I actually did the calculation in SI units - that's what I prefer. But since the original post was written using units of feet and inches, I chose those units, for the aid of Infi.RC.
     
  9. Aug 23, 2004 #8
    I dont understand, why cant we all be on the same page. Somebody should petition against the old british system and make the worldwide measurement scale the metric system.
     
  10. Aug 23, 2004 #9

    Gokul43201

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Americans are never going to get used to liters and meters and grams - NIST has been trying, but IMO it ain't happening.
     
  11. Aug 23, 2004 #10

    pervect

    User Avatar
    Staff Emeritus
    Science Advisor

    Liters are OK for Americans who drink soft drinks :-)
     
  12. Aug 24, 2004 #11
    The air industry doesn't help the metric system. Can you imagine a pilot confusing feet and meters?
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: Need for Speed
Loading...