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Help, about forces

  1. Sep 19, 2004 #1
    I tried doing these but my teacher has not gone over forces yet. Please help.

    1) Two calibrated elevation blocks have a combined thickness of 1.86 cm. Find the angle of elevation of the 1.00-meter long track for this situation.

    2) A block having mass M slides down an inclined plane. THe force of friction between the plane and the inclined plane is f , the block's weight is Mg and the normal force is N . Draw a freebody force diagram showing the forces acting on the block.

    3) For the following position versus time values, calculate the average velocity for each of the four time intervals. What is the physical meaning of a negative average velcity?
    Position (m) 1.24, 1.57, 2.63, 2.25, 2.00
    Time (s) 1.00, 1.74, 2.33, 2.70, 3.00
  2. jcsd
  3. Sep 19, 2004 #2
    I don't quite understand the first question, but I can help you with the next two.
    2) The normal force is acting perpendicular to the surface of the inclined plane( pointing away and up from the inclined plane). Fg points straight down, and the frictional force points parallel to the incline (against the motion of the object).
    3)velocity = distance/time
    -ve velocity simply means an object is travelling in a negative direction.
  4. Sep 19, 2004 #3
    Think the first one is trigonometry:
    The elevation blocks form the side "opposite" to the angle of elevation of length or height 0.0186m

    The 1.00m track is the hypotenuse in this case joining the top of the block to the angle you are looking for.

    So it should be: sin(angle of elevation) = opp/hyp = 0.0186/1.00

    I don't have a calc handy, but the answer should be pretty small.
  5. Sep 19, 2004 #4
    Thanks you guys for all your help!
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