The forces acting on the arm of a person lifting a dumbbell. The force F is the force pulling on the hand due to the weight of the dumbbell, the force Warm is the weight of the arm and T is the tension due to the muscles connecting the arm and the trunk.
Question: Due to Newton's third law we can make the following statement:
The arm exerts on the trunk a force which equals - T.
The weight Warm is equal in magnitude to the tension T.
Forces Warm and T are a action/reaction pair of forces.
Forces Warm and F are a action/reaction pair of forces.
The weight of the arm has no reaction force.
physics - bobpursley, Tuesday, October 6, 2009 at 12:40pm
without a picture, the question makes no sense. Forces are vectors, and have directions.