1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

What is the deceleration of the vehicle?

  1. Oct 18, 2009 #1
    1. I am looking to verify my calculation. Question A vehicle of mass 5Tonnes is travelling with a velocity of 80kmh-1 if it needs to stop within a dstnace of 0.5 km using a constant braking force what is the deceleration of the vehicle



    2. V^2 = 2xSxA, A=V^2 / 2S



    3. A=V^2/2s
    80kmn = 22.222ms
    A=22.222^2/2x500
    A=493.8/1000
    A=0.494
    Deceleration = - 0.494
     
  2. jcsd
  3. Oct 18, 2009 #2

    Redbelly98

    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper

    Re: Deceleration

    Looks good :smile:

    Welcome to PF.
     
  4. Oct 19, 2009 #3
    Re: Deceleration

    appreciated thanks
     
  5. Oct 19, 2009 #4
    Re: Deceleration


    IET (BK) - 0 new messages

    new topic : profile : search : help : dashboard : home

    Latest News: Conditions of use updated; signatures and other forum hints and tips
    Private Messages Buddies Categories: SelectAsk the Chief Executive=== Technical discussions ===Wiring and the regulationsCommunicationsConsumer technologyControl and automationElectronic engineeringInformation technologyInnovations and emerging technologiesManagementManufacturingPowerTransportGeneral professional and technical=== General and career discussions ===FeedbackCEng, IEng, EngTech and other professional registration mattersSavoy Place Virtual ClubStudent and apprentice discussion forum=== Archived categories ===New Institution

    latest topics : statistics

    IET » Student and apprentice discussion forum » Calculation check Topic Title: Calculation check
    Topic Summary: Deceleration
    Created On: 18 October 2009 06:11 PM
    Status: Post and Reply
    Linear : Threading : Single : Branch

    Search Topic
    Keyword


    Topic Tools
    Quick Reply
    Subscribe to this topic
    E-mail this topic
    Bookmark this topic
    View similar topics
    Print this topic.


    18 October 2009 06:11 PM


    BK

    Posts: 11
    Joined: 28 September 2009

    Can anyone give this the once over make sure I have the formula calcs etc right

    Vehicle mass 5 Tonnes travelling with a velocity 80kmh. It needs to stop with in 0.5km using constant braking force

    Deceleration:
    (80kmh = 80x1000/3600 = 22.2m/s)

    a=(v^2-u^2) / 2s
    a=(0-22.2^2)/2x500
    a=(493.83)/1000
    a= 0.494ms
    as Deceleration = -0.49

    Just want to check I am on the right line
    Report this to a Moderator
    Reply : Quote : Top : Bottom : Edit : Delete

    19 October 2009 01:45 PM


    tonysung

    Posts: 579
    Joined: 14 September 2001

    It's a very good start. Perhaps you could add a few explanatory notes to your working so it can be checked properly.

    E.g., "Deceleration80kmh = 80x1000/3600 = 22.2m/s)" should be 'velocity' or 'speed' in m/s.

    Please have another go.

    Kind regards

    -------------------------
    tony sung
    Report this to a Moderator
    Reply : Quote : Top : Bottom

    19 October 2009 07:11 PM


    BK

    Posts: 11
    Joined: 28 September 2009

    Apologies that should have been Velocity 22.2ms

    My concern is whilst working out time taken

    V/A=T, 22.2/0.4938 = 45s

    I checked using a Velocity, Time distance calculator on the net and it calculates 22.5s

    Therefore was I correct in using 2s in my initial calculation, it appears to be correct when I transformed the formula
     
  6. Oct 19, 2009 #5

    Redbelly98

    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper

    Re: Deceleration

    Yes, 2s was correct since the equation is

    v2 = 2 s a​

    22.5 sec would be the time to go 500 m at a constant velocity (no deceleration) of 22.2 m/s. But in that case the vehicle would not come to a stop, as stated in the problem.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook