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

Second law of motion

  1. Nov 19, 2007 #1
    in the newtons second law of motion we study "F=ma" letters having their usual meanings.
    so if any object say"A" comes in the way of a huge object "B", moving with a constant velocity; a=0, doesnt the object "a" feel any force upon him?
  2. jcsd
  3. Nov 19, 2007 #2


    User Avatar
    Science Advisor
    Homework Helper

    When two objects collide, they are in contact for a while. At that time they exert a force on one another and they will accelerate (that is, one will decelerate and the other will accelerate, so in the end the moving one will go slower and the stationary one will be moving = going faster). The amount of time for which they are in contact is usually very short though. Also, we hardly ever need to know exactly how long it is, as problems involving colliding objects can usually be solved by looking at the (kinetic) energies before and after the collision.

    Was that your question?
  4. Nov 19, 2007 #3


    User Avatar
    Science Advisor

    Object A will feel an effective force which is approximately equal to m*v/t


    m = mass of object B
    v = velocity of object B
    t = time of contact
  5. Nov 21, 2007 #4
    that is pretty much an answer i had presumed.
    But,force being a vector quantity has its effect in the direction in which an object accelerates. in the case, when "A" hits "B", "A" accelerates in opp. direction to "B", giving raise to a force in backward direction(the direction from which it is comming). Now how come "B" eperiences force and starts moving along with "A"?
  6. Nov 22, 2007 #5


    User Avatar

    The answer to your question is perhaps Newton's third law? Action - reaction
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: Second law of motion
  1. The second law (Replies: 17)

  2. Second Law (Replies: 9)