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

Homework Help: What force is needed to accelerate a car

  1. Sep 14, 2008 #1
    1. The problem statement, all variables and given/known data

    What force is needed to make a 1200kg vehicle accelerate from rest to 108km/hr in 100m

    2. Relevant equations

    aceleration = Velocity/time

    Force = Mass x Acceleration

    Time = Distance/Velocity

    3. The attempt at a solution

    M = 1200kg

    D = 100m

    V = 108 km/hr / 3.6 = 30 m/s

    t = 100m/30 m/s = 3.33sec

    a = 30 m/s / 3.33sec = 9 m/s

    F = 1200 x 9 m/s = 10800kg

    Now do I need to convert the kg to Newtons? by multiplying by gravity 9.8m/s I am a bit confused about that?
     
  2. jcsd
  3. Sep 14, 2008 #2

    danago

    User Avatar
    Gold Member

    Be careful with how you calculated the time of the trip.

    You used t=s/v, but that equation is for the case when the acceleration is zero.

    The velocity of the car isnt 30m/s for the whole trip, only at the end.
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook