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: Forces on a box

  1. Dec 18, 2007 #1
    A box is sitting on the floor of a truck. The truck accelerates away from a stoplight. Which statement most accurately describes forces on the box.

    A) The box is pushed forward by the force of friction acting in the direction of motion of the truck.

    B)The engine of the truck pushes the box backward as it slides across the floor of the truck.

    C) The acceleration of ofrce on the box pushes it toward the rear of the truck.

    D) The acceleration force on the box is canceled out by the frictional force exerted by the bed of the truck.

    E)None of the above

    during the test i picked C...is that right?
    1. The problem statement, all variables and given/known data

    2. Relevant equations

    3. The attempt at a solution
    Last edited by a moderator: Dec 18, 2007
  2. jcsd
  3. Dec 18, 2007 #2


    User Avatar

    Staff: Mentor

    I don't think C is the correct answer. Think about the situation from the perspective of the box, and carefully re-read the possible answers.
  4. Dec 18, 2007 #3
    well what about in a traffic light and when you hit the gas, the things in your car move backward, and when you hit the break that's when the things move forward
  5. Dec 18, 2007 #4


    User Avatar

    Staff: Mentor

    No, for this problem, you need to think of how the box moves (and why) with respect to the Earth, not with respect to the moving reference frame of the car.

    When you accelerate away from a light, what is the motion of the box with respect to the ground? Why does it move that way?
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook