1. Not finding help here? Sign up for a free 30min 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!

Kinematics and magnitude problem

  1. Nov 29, 2004 #1
    What is the magnitude of velocity of an object after free falling from rest after 3 minutes?
    (A) 9.8 m/s (D) 180 m/s
    (B) 32 m/s (E) 1800 m/s
    (C) 87 m/s

    I think the answer is 1800 m/s but I'm not sure how to arrive at it.
     
  2. jcsd
  3. Nov 29, 2004 #2

    arildno

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    Dearly Missed

    Well, what equation would you use?
     
  4. Nov 29, 2004 #3
    I have no idea, the equations that we studied in this chapter don't seem to work with this problem.
     
  5. Nov 29, 2004 #4

    arildno

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    Dearly Missed

    What does free fall mean?
     
  6. Nov 29, 2004 #5
    it's falling without a drag-producing device like a parachute
     
  7. Nov 29, 2004 #6
    Have you tried transfering your minutes into seconds before putting everything into your formula?
     
  8. Nov 29, 2004 #7
    I don't even know what formula to use. I'm in an AP class that my teacher doesn't show up to. He just assigns us homework and shows us videos. The book isn't much help at all so I'm completely lost.
     
  9. Nov 29, 2004 #8
    If those are the only questions you have I'd just ask someone before you have to return the assignment. The formula is probably fairly straight forward and easily explainable. Afterwards you can just do the other questions quickly.

    If your book has the answer in the back I might be able to determine the formula.
     
  10. Nov 29, 2004 #9
    no answers...
     
  11. Nov 29, 2004 #10

    Doc Al

    User Avatar

    Staff: Mentor

    Hint: What is the meaning of "acceleration due to gravity"?
     
  12. Nov 29, 2004 #11
    the pull of gravity causes objects to accelerate towards the ground... that doesn't really help me
     
  13. Nov 29, 2004 #12

    Doc Al

    User Avatar

    Staff: Mentor

    It would help you if you know what acceleration means. What's the definition of acceleration?

    And what is the acceleration due to gravity?
     
  14. Nov 29, 2004 #13
    You're right, it would help, but like I said, I really don't know. : /
     
  15. Nov 29, 2004 #14

    Doc Al

    User Avatar

    Staff: Mentor

    Acceleration is the rate of change of velocity; the acceleration due to gravity is 9.8 [itex]m/s^2[/itex].
     
  16. Nov 29, 2004 #15
    hi,
    you could try using this equation
    [tex]v=u+at[/tex] where v is the final velocity and u is the initial velocity
    t is the time in seconds
    a is acceleration
    in your case a=9.8m/s^2
    t=3*60 seconds = 180 seconds
    now pop in the numbers and out will pop the answer
     
  17. Nov 30, 2004 #16
    Actually, considering the options he was given, I'd say in his course the acceleration due to gravity is used as [tex]10\ m/s^2[/tex]
     
  18. Dec 2, 2004 #17
    "he"? :frown: I'd hope not...
     
  19. Dec 4, 2004 #18
    Question:
    What is the magnitude of velocity of an object after free falling from rest after 3 minutes?

    Solution:
    Time:180s <----(3)(60) to convert to seconds
    Acceleration:[tex]9.8m/s^2[/tex] <---- Gravitational Force on Earth
    D=(A)(T)
    D=(9.8)(180s)

    Answer:
    1764m

    I might be wrong

    *Edit: When I read my post again, I got confused, are you trying to find out the distance?
     
  20. Dec 4, 2004 #19
    Here since the object is falling freely from rest, initial velocity(u) is zero. So now you have to find the final velocity(v). Use v = u + at, where a= [tex]9.8m/s^2[/tex]. So your answer is right. If you want to calculate distance, then use [tex]s = ut + {1 \over 2}a t^2 [/tex].
     
  21. Dec 4, 2004 #20

    tony873004

    User Avatar
    Science Advisor
    Gold Member

    A car goes from 0 to 60 in 8 seconds. If it could keep up this acceleration, how fast would it be going in 16 seconds?

    Do your problem the same way.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: Kinematics and magnitude problem
  1. Kinematics Problems (Replies: 4)

  2. Kinematic problem (Replies: 1)

  3. Kinematics Problem (Replies: 2)

Loading...