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.
without a picture, the question makes no sense. Forces are vectors, and have directions.
The correct statement due to Newton's third law is:
Forces Warm and T are an action/reaction pair of forces.
Newton's third law states that for every action, there is an equal and opposite reaction. In this case, the force exerted by the arm on the trunk (Warm) and the tension force (T) in the muscles are an action-reaction pair.
The correct statement due to Newton's third law in this scenario is:
"Forces Warm and T are an action/reaction pair of forces."
To understand this, let's break down the forces acting on the arm of a person lifting a dumbbell:
1. The force F is the force pulling on the hand due to the weight of the dumbbell. This force is acting downward.
2. The force Warm is the weight of the arm. This force is also acting downward.
3. The tension force T is due to the muscles connecting the arm and the trunk. This force is acting upward.
According to Newton's third law, for every action, there is an equal and opposite reaction. Therefore, the action and reaction forces form pairs. In this case, the force Warm (action) and the force T (reaction) are an action/reaction pair. These forces have equal magnitudes but act in opposite directions.
The other options listed in the question are incorrect:
- The arm exerts on the trunk a force which equals - T: This statement is not valid because the arm exerts a force equal in magnitude but in the opposite direction to T, not -T.
- The weight Warm is equal in magnitude to the tension T: While both forces have equal magnitudes, they are acting in opposite directions, so they cannot be equal.
- Forces Warm and F are an action/reaction pair of forces: The force Warm is a force due to the weight of the arm, while the force F is due to the weight of the dumbbell. These forces are not an action/reaction pair since they are acting in different directions.
- The weight of the arm has no reaction force: This statement is incorrect. The weight of the arm is counteracted by the tension force T, which is the reaction force.