Performing a medical examination assessing the conduction of nerves, a physician sends an electric impulse down the forearm of a patient. What is the average velocity of the electric signal if it arrives at an electrode 25 cm away from its initial position following 5 ms of travel?

Question

Performing a medical examination assessing the conduction of nerves, a physician sends an electric impulse down the forearm of a patient.  What is the average velocity of the electric signal if it arrives at an electrode 25 cm away from its initial position following 5 ms of travel?

Quizplus · Accepted Answer

11ecba2d_130a_c3dd_a3bf_63cfe79d330d_MD0008_00 In translational motion, displacement refers to the difference between the final and initial position of an object. Unlike distance, displacement is a vector quantity that contains both magnitude and direction. Displacement is also path-independent and can be determined by knowing only the initial and final position of an object (ie, the path along which an object travels is irrelevant). Velocity (v), a vector quantity that expresses displacement per unit time, can be assessed instantaneously or as an average. Instantaneous velocity refers to the momentary velocity of an object at a single point in time. Alternatively, average velocity refers to the mean velocity of an object over a period of time. The motion of an object over a period of time can be expressed as an average velocity on an x,y-coordinate system by dividing the x- and y-components of displacement (x_f− x_i and y_f− y_i, respectively) by the interval of time (t) for that motion: 11ecba2d_130a_c3de_a3bf_c5e39c154a9e_MD0008_00 In this question, a medical practitioner investigates the function of nerves by eliciting the flow of electrons down a patient's nerve. Although the electrons follow a winding course through the forearm, the total displacement of the electrons during the 5 ms journey is 25 cm. By selecting an x,y-coordinate system oriented such that the motion of the electrons takes place along the x-axis exclusively (no y-axis displacement, v_y = 0), only the x-component of average velocity v_x must be considered. Substitution of displacement and time values into the equation for displacement yields: 11ecba2d_130a_c3df_a3bf_618c4717a159_MD0008_00 Converting all values to standard units results in: 11ecba2d_130a_eaf0_a3bf_55fe6f4bf88e_MD0008_00 Therefore, it can be concluded that the average velocity of electrons that travel down the patient's arm is 50 m/s. Educational objective: The average velocity of an object undergoing translational motion can be calculated as the total displacement of that object divided by the interval of time for that motion. Displacement and velocity are both vector quantities.

Performing a Medical Examination Assessing the Conduction of Nerves, a Physician