Results 1 to 9 of 9

Thread: Physical Science II - Mph of a dragster at the finish line of a race- ?

  1. #1

    Physical Science II - Mph of a dragster at the finish line of a race- ?

    Please assist me with the following question :


    One "G" of acceleration is the rate at which an object will accelerate if it is dropped near the Earth's surface, ignoring air resistance. One "G" of force is the force necessary to generate one G of acceleration (although "G" is not an official SI unit of force).

    Suppose you built a rocket-powered dragster which could produce a constant acceleration, for a few seconds, that was similar to the acceleration that Cmdr Shepard experienced for the first several minutes of his flight.
    On one pass, your dragster produces a constant acceleration of exactly 5.97 G's throughout the whole race.
    How fast would your dragster be going at the end of a drag strip that was exactly 1000 feet long?
    Your answer must be in miles/hour.

    The work I did so far is:
    √2(58.506 m/s˛)(1000m) = 342.07016824 m/s˛ converted to MPH = 765.1892 rounded to 765 MPH


    Capture.jpg

  2. #2
    Elite Member
    Join Date
    Jun 2007
    Posts
    17,195
    Quote Originally Posted by student_2018 View Post
    Please assist me with the following question :


    One "G" of acceleration is the rate at which an object will accelerate if it is dropped near the Earth's surface, ignoring air resistance. One "G" of force is the force necessary to generate one G of acceleration (although "G" is not an official SI unit of force).

    Suppose you built a rocket-powered dragster which could produce a constant acceleration, for a few seconds, that was similar to the acceleration that Cmdr Shepard experienced for the first several minutes of his flight.
    On one pass, your dragster produces a constant acceleration of exactly 5.97 G's throughout the whole race.
    How fast would your dragster be going at the end of a drag strip that was exactly 1000 feet long?
    Your answer must be in miles/hour.

    The work I did so far is:
    √2(58.506 m/s˛)(1000m) = 342.07016824 m/s˛ converted to MPH = 765.1892 rounded to 765 MPH


    Capture.jpg
    Why did you assume a = 6*g (instead of 5.97*g)? And:

    Dx = 1000 ft = 304.8 meters
    “... mathematics is only the art of saying the same thing in different words” - B. Russell

  3. #3
    The picture was an example from the book on how to solve the problem. I can't figure it out

  4. #4
    Elite Member
    Join Date
    Jun 2007
    Posts
    17,195
    Quote Originally Posted by student_2018 View Post
    The picture was an example from the book on how to solve the problem. I can't figure it out
    Did you adjust for the length to be converted to meters?
    “... mathematics is only the art of saying the same thing in different words” - B. Russell

  5. #5
    New Member Whutever42's Avatar
    Join Date
    Jan 2018
    Location
    A Flat Earth
    Posts
    14
    Instead of making G into metric units and having to convert the 1000ft into meters use 32ft/sec2 and you would only have to convert ft/sec into miles/hour

  6. #6
    New Member chris84567's Avatar
    Join Date
    Jan 2018
    Location
    A Concave Earth
    Posts
    12
    vf2=vi2+2ad
    vi is 0
    vf is what you are looking for
    a is g*5.97 or 5.97*32=191 feet per second2 (stop being a commy and use some english units)
    d is 1000 feet

    vf=sqrt(2*191*1000) feet/second
    vf=618 feet/second

    Convert to mph

    618 feet/second * 1 mile/5280feet * 3600 hour/ 1 second = 421 mph
    Last edited by chris84567; 02-13-2018 at 12:13 PM. Reason: had 100 instead of 1000 feet

  7. #7
    Junior Member
    Join Date
    Jan 2018
    Location
    Toronto
    Posts
    62
    Quote Originally Posted by chris84567 View Post
    vf2=vi2+2ad
    vi is 0
    vf is what you are looking for
    a is g*5.97 or 5.97*32=191 feet per second2 (stop being a commy and use some english units)
    d is 1000 feet

    vf=sqrt(2*191*1000) feet/second
    vf=618 feet/second

    Convert to mph

    618 feet/second * 1 mile/5280feet * 3600 hour/ 1 second = 421 mph
    1) It's commie

    2) You guys are the worst for still using Imperial units, and the OP's teacher is a sadist for assigning a problem with mixed units

    3) You can guide posters towards a solution, but don't do people's homework for them on this site; they don't learn any physics or math if you just provide them with the solution.

  8. #8
    New Member chris84567's Avatar
    Join Date
    Jan 2018
    Location
    A Concave Earth
    Posts
    12
    Quote Originally Posted by j-astron View Post
    2) You guys are the worst for still using Imperial units, and the OP's teacher is a sadist for assigning a problem with mixed units
    there are no mixed units

    if you cant use both systems of measurement you obviously don't understand the problem

  9. #9
    Junior Member
    Join Date
    Jan 2018
    Location
    Toronto
    Posts
    62
    Quote Originally Posted by chris84567 View Post
    there are no mixed units

    if you cant use both systems of measurement you obviously don't understand the problem
    Uh, ok. Check your assumptions at the door. I understand the problem fine, and can use both systems of measurement fine. The Imperial one is just mostly stupid and outdated, because there are arcane conversion factors between different units of the same dimension (e.g feet to miles), rather than multiples of 10. And the rest of the world has adopted an international standard.

    The fact that OP only seemed to know the value of g in SI units and substituted that in, despite the fact that the other units in the problem were given in Imperial, suggested to me that maybe his/her teacher was mixing and matching unit systems. Pick one system and stick to it. Either way, I was being mostly facetious with my points 1 and 2. My point 3 was the one that was actually important, i.e. in the future please do not provide complete solutions to problems on this site.

Tags for this Thread

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •