1. Limited time only! Sign up for a free 30min personal 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!

Homework Help: Simple Power calculation

  1. Mar 7, 2012 #1
    Can anyone see where i have went wrong? I keep getting the same wrong answer.

    A 1100 kg car accelerates from rest reaching a distance of 110 m in 8.7 seconds, determine the average power in KW required to achieve this acceleration (your answer should be to 2 decimal places).

    ANS = 40.43
    MY ANS = 20.21

    Working out

    V = d/t
    V= 110/8.7 = 12.64

    Acc = (12.64 - 0) / 8.7 = 1.45

    Force = ma
    Force = 1100 x 1.45 = 1598.63

    Work done = force x distance
    Work done = 1598.63 x 110 = 175848

    Power = WD/T
    Power = 175848/8.7 = 20.21KW

    Thanks
     
  2. jcsd
  3. Mar 7, 2012 #2
    The velocity is not constant here,
    you should use s = ut + [itex]\frac{1}{2}[/itex]at2 instead
     
  4. Mar 7, 2012 #3
    Thanks for your reply.
    How do i use this formula if i have two unknowns for V and a
     
  5. Mar 7, 2012 #4
    You just have to find a and carry on with F=ma

    P.S. I gave you the wrong formula just now :P
     
  6. Mar 7, 2012 #5
    Got it, thanks mate
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook