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: Help with F=ma

  1. Apr 6, 2010 #1
    Each of the four wheels of a car pushes on the road with a force of 4.0 x 10³ N [down]. The driving force on the car is 8.0 x 10³ N [W]. The frictional resistance on the car is 6.0 x 10³ N [E]. Calculate the following:
    (a) mass of the car
    (b) net force on the car
    (c) car's acceleration

    For Fnet, would u also add 4(4.0 x 10³ N [up]) to the rest of vectors to cancel out the force all the tires have on the road? Or:
    8.0 x 10³ N [W] + 6.0 x 10³ N [E]= 2.0 x 10³ N [W]

    2.0 x 10³ N [W] + 4(4.0 x 10³ N [down])= Fnet
    ?!

    I just did all that on my phone.. I'm desperate for some help :(
     
  2. jcsd
  3. Apr 6, 2010 #2

    rock.freak667

    User Avatar
    Homework Helper

    Re: F=ma

    I am led to believe that the entire mass of the car is supported by the wheels alone.

    So yes the entire weight is 4(4x103) N, so the mass of the car is ?
     
  4. Apr 6, 2010 #3
    Re: F=ma

    m= 1.6 x 104 N

    but what about Fnet
     
  5. Apr 6, 2010 #4

    rock.freak667

    User Avatar
    Homework Helper

    Re: F=ma

    There is a driving force and a resistance to the driving force, so what should be the net force between these two?
     
  6. Apr 6, 2010 #5
    Re: F=ma

    so i don't have to worry about the force of the tires on the road?

    Fnet=8.0 x 10³ N [W] + 6.0 x 10³ N [E]
    Fnet= 2.0 x 10³ N [W]
     
  7. Apr 6, 2010 #6

    rock.freak667

    User Avatar
    Homework Helper

    Re: F=ma

    you mean negative here


    But yes that should be correct.
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook