When an athlete holds a barbell overhead, the reaction force is the weight of the barbell on his hand. how does this force vary
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Answer:
Explanation:
For an object to move with constant velocity, the acceleration of the object must be zero:
.
As the net force equals acceleration multiplied by mass , this must mean:
.
So, the sum of the three forces must be zero:
,
this implies:
.
To obtain this sum, its easier to work in Cartesian representation.
First we need to define an Frame of reference. Lets put the x axis unit vector pointing east, with the y axis unit vector
pointing south, so the positive angle is south of east. For this, we got for the first force:
,
as is pointing north, and for the second force:
,
as is pointing west.
Now, our third force will be:
But, we need the magnitude and the direction.
To find the magnitude, we can use the Pythagorean theorem.
this is the magnitude.
To find the direction, we can use:
and this is the angle south of east.