Question

a person is cold and rubs his or her hands together. when the persons hands are pressed together at a constant force and moved back and forth, heat is generated. what happens to the speed of the hands as the persons amount of friction from pressing increases? it increases. it decreases. it increases and then decreases. it remains constant.

Explanation:

Step1: Recall friction - force relationship

Friction opposes relative motion. When friction increases while the applied force to move hands is assumed to be constant (since no change in pushing - moving effort is mentioned other than the change in pressing), the net force available for motion decreases.

Step2: Apply Newton's second law

According to Newton's second law $F = ma$, where $F$ is the net force, $m$ is the mass of the hands (which is constant), and $a$ is the acceleration. As the net force $F$ decreases, the acceleration $a$ decreases. A decrease in acceleration over time leads to a decrease in speed if the hands were in motion.

Answer:

It decreases.