Results 1 to 2 of 2

Math Help - physics help please, FORCES WORKING TOGETHER.

  1. #1
    Newbie
    Joined
    Apr 2008
    Posts
    1

    Exclamation physics help please, FORCES WORKING TOGETHER.

    Two cars, travelling at the same speed, are involved in separate crashes. driver A is 100kg and driving an old car with 'fixed' seat belts. he decelerates from 30 m/s to rest in 1 second.
    Driver B is also 100 kg, but driving a car with more modern 'inertia-type' seat belts. these seat belts extend slightly before bringing the driver to a stop, so they bring the driver to a stop more slowly. driver B decelerates from 30m/s to rest in 3 seconds.

    a) calculate the deceleration of both drivers, show your working.
    --> I did: driver A: 30-1/10 = 29.9 m/s 2
    driver B: 30-3/10= 29.7 m/s 2

    Is this the right answer?

    b) calculate the force exerted by the seat belts on both drivers.
    c) explain why the 'inertia-type' seat belts are safer to way.
    d) how might this 'theory' be used to design crash barriers on motorways or at racing circuits ?

    I understood the b) but to do it I need to be sure the a) is correct.
    thanks!
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Forum Admin topsquark's Avatar
    Joined
    Jan 2006
    From
    Wellsville, NY
    Posts
    9,817
    Thanks
    316
    Awards
    1
    Quote Originally Posted by soledadS27 View Post
    Two cars, travelling at the same speed, are involved in separate crashes. driver A is 100kg and driving an old car with 'fixed' seat belts. he decelerates from 30 m/s to rest in 1 second.
    Driver B is also 100 kg, but driving a car with more modern 'inertia-type' seat belts. these seat belts extend slightly before bringing the driver to a stop, so they bring the driver to a stop more slowly. driver B decelerates from 30m/s to rest in 3 seconds.

    a) calculate the deceleration of both drivers, show your working.
    --> I did: driver A: 30-1/10 = 29.9 m/s 2
    driver B: 30-3/10= 29.7 m/s 2

    Is this the right answer?
    For driver A you have an initial speed of 30 m/s and a final speed of 0 m/s in a time of 1 s.
    a = \frac{\Delta v}{\Delta t} = \frac{0~m/s - 30~m/s}{1~s} = -30~m/s^2
    (The negative sign merely indicates that the direction of the acceleration is opposite the direction of the initial velocity: it is slowing down.)

    You can do the same for driver B.

    -Dan
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. 2D physics forces for circular objects
    Posted in the Algebra Forum
    Replies: 0
    Last Post: March 5th 2012, 04:14 PM
  2. physics forces
    Posted in the Math Topics Forum
    Replies: 2
    Last Post: June 29th 2009, 11:25 PM
  3. Physics: Electrostatic Forces question
    Posted in the Math Topics Forum
    Replies: 6
    Last Post: March 6th 2009, 08:42 PM
  4. Physics Forces Question
    Posted in the Math Topics Forum
    Replies: 2
    Last Post: January 25th 2009, 11:29 AM
  5. physics w/ Forces
    Posted in the Math Topics Forum
    Replies: 1
    Last Post: October 26th 2007, 07:23 AM

Search Tags


/mathhelpforum @mathhelpforum