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: Wording of a Force and Motion problem

  1. Jun 13, 2010 #1
    These are my forte... questions that make you feel dumb when you spend 20 minutes just thinking about what the hell they're asking... and then make you feel dumber once you figure out the simplicity of the answer...

    Here we go, this has to do with the wording of the problem. To me a) and b), ask the same thing as c) and d)... but apparently I'm wrong.

    Firefighter (712N) sliding down a pole...

    a) asks for the magnitude and b) asks for the direction "of the vertical force on the firefighter from the pole."

    c) asks for the magnitude and d) asks for the direction "of the vertical force of the pole on the firefighter."

    I have figured out a) and b), b) being upwards. [a) is 494N which I'll reference later.]
    The book says that c) has the same magnitude as a), but that d) is in the opposite direction (down).

    Now I have looked at the problem like this:
    a) and b) are asking about the force that the pole is exerting on the firefighter, and since it is slowing him down, it would be in the upwards direction.

    Say that c) and d) are asking for the force that the firefighter exerts on the pole (I assume this because the answer says that the direction is down), this makes sense because the force the firefighter exerts on the pole would equal the force the pole exerts on the firefighter, and as a system, the remaining force is what propels the downward motion (that left over from the restriction of the upward force against the gravity).

    Am I wrong to way that the book has worded this question correctly, and that the quoted and underlined sentences above are asking for the same information?

    Thanks all!
     
  2. jcsd
  3. Jun 14, 2010 #2
    The wording is clearly wrong.
    I'm sure the question meant to ask you about the Newton's 3rd Law pair of forces.
    One is the vertical force of the pole on the firefighter, and the other is the vertical force of the firefighter on the pole.
     
  4. Jun 14, 2010 #3
    Thank you, I thought I was crazy on this one.
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook