If you are holding a dumbbell in your hand, there are three forces acting, Weight of the arm pulling the arm down, a tension force that the muscle in the shoulder exerts on the arm, and the force that the dumbbell exerts on the fist.. which of these forces are contact forces?
some help would be appreciated!
Since all the objects and the muscles are touching each other to apply a force, all three are contact forces.
Non-contact forces can be applied at a distance, such as force of gravity, magnetic forces, etc.
See also:
http://en.wikipedia.org/wiki/Contact_force
To determine which of these forces are contact forces, we need to understand the concept of contact forces. Contact forces are forces that arise due to physical contact between two objects. They can occur when two objects push, pull, or press against each other.
In this scenario, the three forces acting on the dumbbell being held in your hand are:
1. Weight of the arm: This force is the gravitational force acting on the arm due to its mass. It is directed downward and can be considered as a non-contact force because it is the result of the gravitational pull of the Earth on the arm. This force does not require direct physical contact with the dumbbell.
2. Tension force from the muscle: When you hold the dumbbell, your muscles contract to generate the necessary force to hold it up. The tension force exerted by the muscles on the arm is a contact force. It is transmitted through the bones, tendons, and ligaments, creating a physical contact between these body parts.
3. Force exerted by the dumbbell on the fist: This force is the reaction force to the force exerted by the muscles on the dumbbell. Since the dumbbell is in direct physical contact with your fist, the force it applies can be considered a contact force.
In summary, the tension force exerted by the muscles and the force exerted by the dumbbell on the fist are the contact forces in this scenario. The weight of the arm is a non-contact force since it arises due to gravity.