# Physics Resultant Force

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

(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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