A uniform rod is attached by a hinge at one end to a wall. The other end of the rod is supported by a wire so that the rod is horizontal and in equilibrium.
Which arrow shows the direction of the force on the rod from the hinge?
ANSWER: D
The Physics Behind
- The first condition of equilibrium states that the sum of all forces on object is zero.
- This means that
- the sum of forces along the vertical is zero
- the sum of forces along the horizontal is also zero
- Along the vertical, the weight is cancelled by the vertical component of the tension in the wire and upward component of the force from the hinge [let's call it Y]. You can realize that this indeed the case when you use the second condition of equilibrium.
- Along the horizontal, the horizontal component of tension is cancelled by the horizontal force exerted by the hinge [let's call it X].
- These upward Y and rightward X gives us the idea that the direction should be that in D.
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