Physics Resultant Force

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Suppose F is the resultant of F1 and F2.Find the missing F2.

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  • 8 年前
    最愛解答

    There are 3 forces involved F1, F2 and F.

    Assume the forces are drawn on the x and y co-ordinates system, one unit represents a force of 1 Newton.

    The point where the force F1 and F meet is the origin (0, 0) of co-ordinates system.

    The line joining the points (0, 0) and (-2, 2) is force F1

    The line joining the points (0, 0) (2, 5) is The resultant force F

    This Force is the same as the line joining (0, 0) and (-2, -5).

    They both have same magnitude and same direction.

    Assuming all 3 forces involved acting on the same point (0, 0)

    Resolve all the forces in x (horizontal) and y (vertical) directions.

    Along the x-axis,

    Force F1x = -2N (towards West)

    Resultant force Fx = -2N (towards West)

    F2x = unknown

    Fx = F1x + F2x

    -2N = -2N +F2x

    F2x = +2N - 2N

    F2x = 0 N

    Along the y-axis,

    Force F1y = +2N (towards North or upwards)

    Resultant force Fy = -5 N (towards South, or downwards)

    F2y = unknown

    Fy = F1y + F2y

    - 5N = + 2N + F2y

    F2y = -5N –2N

    F2y = - 7N

    Negative sign indicates towards South, or downwards

    (F2)^2 = (F2x)^2 + (F2y)^2

    (F2)^2 = (0)^2 + (-7N)^2

    (F2)^2 = (0 + 49) Newton^2

    F2 = = - [square root of 49) N, direction pointing South

    F2 = - 7N pointing South (i.e. downwards)

    This force F2 is perpendicular to x-axis

    Hence force F2 is 7 Newton downward. This force acts along the y-axis on the diagram. The arrow is downwards.

    .

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