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Newtons Law / Kinematic problem?

  1. Nov 15, 2006 #1
    Hello, the question I'm having trouble with is:

    "A 8.00kg block of ice, released from rest at the top of a 1.5 m long frictionless ramp, slides downhill, reaching a speed of 2.5 m/s at the bottom.
    What is the angle between the ramp and the horizontal?"

    My first attempt to solve this problem was that I would use kinematics to get the acceleration. And then use the acceleration and newton's laws to find the angle. By using kinematics I got the equation 2.5^2 = 0 + 2(a)(1.5)
    I then got a to be 1.64. Using that I set the equation 8gsin(theta) = 1.64(8). Eventually getting theta to equal 9.6 degrees. But when I compared my answer to the a fellow classmate He got 12.275, but I can't really follow his work and theres no answer in the back of the book, so can anyone help?
     
  2. jcsd
  3. Nov 15, 2006 #2

    Hootenanny

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    Since there is no friction, it may be easier to consider this problem as a conservation of energy problem.
     
  4. Nov 15, 2006 #3
    We have not gotten to energy yet in my class :(. This is the third chapter all we have done is kinematics, projectile motion, and now this.
     
  5. Nov 15, 2006 #4

    Hootenanny

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    I've just looked through your work and it appears it's just your arithmetic that's letting you down. Your kinematic equation is correct, but your value for acceleration is not; try solving for acceleration again.
     
  6. Nov 15, 2006 #5
    Ah jeez I'm so dumb thanks alot! I just have sloppy hand writting so I turned the 1.5 into a 1.9 which gave me the wrong answer thanks alot.
     
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