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Newton's Second Law

  1. Nov 16, 2008 #1
    1. The problem statement, all variables and given/known data
    Trial distance force(N) time(S)
    1 5 15 6.13
    10 15 8.57
    15 15 11.09
    2 5 15 8.40
    10 15 12.98
    15 15 16.39
    3 5 15 6.82
    10 15 9.52
    15 15 12.57
    Trial distance force(N) time(S)
    1 5 20 5.63
    10 20 8.07
    15 20 9.92
    2 5 20 6.04
    10 20 8.98
    15 20 11.45
    3 5 20 5.62
    10 20 8.02
    15 20 10.09
    2. Relevant equations
    1. Until time of Galileo, people believed that a constant force is required to produce a constant speed. Do your observation confirm or reject this notion?
    2. What happnes to the speed as you proceed farther and farther along the measured distances?
    3. What happnes to the rate of increase in speed - the acceleartion - as your proceed farther and farther along the measured distances?
    4. When the force is the same, how does the acceleration depend upon the masS?
    5. When the mass of the skater is the same, how does the acceleration depend upon the force?
    6. Suppose a 3-N force is applied to the skater and no movement results. How can this be explained?

    3. The attempt at a solution
    1. .. I have no idea.
    2. The speed accelerates as I proceed farther and farther.
    3. .. I have no idea. Isn't this same as number 2 tho?
    4. Whoever has more mass has lower acceleration compare to the one who has lower mass.
    5. More force will shorter the rates of acceleration.
    6. No idea.

    Well, guys..
    I tried my best.
    Some of them, I do not know.
    Can you help me with the problems that I didn't know and check the answers for me?
    Thank you so much.
  2. jcsd
  3. Nov 17, 2008 #2
    Well I don't understand what your data is describing but anyways

    1. A Constant force is only required if the force is counter-acting friction in the opposite direction of motion. if you draw a force body diagram and all the forces are equal and opposite of each other (equilibrium) then there is no net acceleration and the object will keep moving at whatever speed/direction it was going

    2. If you are applying a constant force to an object in the direction of motion and this force is greater than friction your object will accelerate. so the longer the time the force acts, the more acceleration, so your speed will increase more and more

    3. If air resistance is negligible your speed should increase by a regular interval every second (assuming that your force remains constant)

    6. If you draw a force body diagram your will find that there are 4 forces acting on your skater: 1. A downward force equal to the skater's mass times acceleration due to gravity, 2. an upward force equal to the previous force (assuming the skater is not sinking), 3. your 3 newton force we shall say to the left, and 4. a frictional force to the right.

    Your frictional force to the right is equal to the static coefficient of friction times the normal force (mg). so if your skater weighs too much, or your coefficient of friction is too high, your 3 N force will not be sufficient to move your skater
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