Automatic sliding doors The first automatic sliding doors were described by Hero of Alexandria almost 2000 years ago. The doors were moved by hanging containers that were filled with water. Modern sliding doors open or close automatically. They are equiped with sensors that detect the proximity of a person and an electromic circuit that processes the signals from the sensors and drives the electomotor-based system that moves the doors. The sensors typically emit pulses of infrared light or ultrasound and detect the reflected pulses. By measuring the delay between emitted and received pulses, the system can determine the distance to the object from which the pulse was reflected. The whole system must be carefully designed to ensure safe and accurate functioning. Designers of such doors take into account several variables such as typical walking speeds of people and their dimensions. Let’s try to learn more about automatic sliding doors by analyzing the motion of a single-side automatic sliding door when a person is walking through the door. Figure 2.30 shows the position-versus-time graph of the motion of the edge of the door (marked with a red cross in the photo) from the moment the door starts opening to when the door is closed while a person walks toward and through the door. The doors are adjusted to start opening when a person is 2.0 m away. What is the average opening speed of the door? a. 0.1 m/s b. 0.3 m/s c. 0.6 m/s d. 3.0 m/s
Automatic sliding doors The first automatic sliding doors were described by Hero of Alexandria almost 2000 years ago. The doors were moved by hanging containers that were filled with water. Modern sliding doors open or close automatically. They are equiped with sensors that detect the proximity of a person and an electromic circuit that processes the signals from the sensors and drives the electomotor-based system that moves the doors. The sensors typically emit pulses of infrared light or ultrasound and detect the reflected pulses. By measuring the delay between emitted and received pulses, the system can determine the distance to the object from which the pulse was reflected. The whole system must be carefully designed to ensure safe and accurate functioning. Designers of such doors take into account several variables such as typical walking speeds of people and their dimensions. Let’s try to learn more about automatic sliding doors by analyzing the motion of a single-side automatic sliding door when a person is walking through the door. Figure 2.30 shows the position-versus-time graph of the motion of the edge of the door (marked with a red cross in the photo) from the moment the door starts opening to when the door is closed while a person walks toward and through the door. The doors are adjusted to start opening when a person is 2.0 m away. What is the average opening speed of the door? a. 0.1 m/s b. 0.3 m/s c. 0.6 m/s d. 3.0 m/s
Automatic sliding doors The first automatic sliding doors were described by Hero of Alexandria almost 2000 years ago. The doors were moved by hanging containers that were filled with water. Modern sliding doors open or close automatically. They are equiped with sensors that detect the proximity of a person and an electromic circuit that processes the signals from the sensors and drives the electomotor-based system that moves the doors. The sensors typically emit pulses of infrared light or ultrasound and detect the reflected pulses. By measuring the delay between emitted and received pulses, the system can determine the distance to the object from which the pulse was reflected. The whole system must be carefully designed to ensure safe and accurate functioning. Designers of such doors take into account several variables such as typical walking speeds of people and their dimensions.
Let’s try to learn more about automatic sliding doors by analyzing the motion of a single-side automatic sliding door when a person is walking through the door. Figure 2.30 shows the position-versus-time graph of the motion of the edge of the door (marked with a red cross in the photo) from the moment the door starts opening to when the door is closed while a person walks toward and through the door. The doors are adjusted to start opening when a person is 2.0 m away.
Three slits, each separated from its neighbor by d = 0.06 mm, are illuminated by a coherent light source of
wavelength 550 nm. The slits are extremely narrow. A screen is located L = 2.5 m from the slits. The
intensity on the centerline is 0.05 W. Consider a location on the screen x = 1.72 cm from the centerline.
a) Draw the phasors, according to the phasor model for the addition of harmonic waves, appropriate for this
location.
b) From the phasor diagram, calculate the intensity of light at this location.
A Jamin interferometer is a device for measuring or for comparing the indices of refraction of gases. A beam
of monochromatic light is split into two parts, each of which is directed along the axis of a separate cylindrical
tube before being recombined into a single beam that is viewed through a telescope. Suppose we are given the
following,
•
Length of each tube is L = 0.4 m.
• λ= 598 nm.
Both tubes are initially evacuated, and constructive interference is observed in the center of the field of view. As
air is slowly let into one of the tubes, the central field of view changes dark and back to bright a total of 198
times.
(a) What is the index of refraction for air?
(b) If the fringes can be counted to ±0.25 fringe, where one fringe is equivalent to one complete cycle of
intensity variation at the center of the field of view, to what accuracy can the index of refraction of air be
determined by this experiment?
1. An arrangement of three charges is shown below where q₁ = 1.6 × 10-19 C, q2 = -1.6×10-19 C,
and q3 3.2 x 10-19 C.
2 cm
Y
93
92
91
X
3 cm
(a) Calculate the magnitude and direction of the net force on q₁.
(b) Sketch the direction of the forces on qi
Chapter 2 Solutions
College Physics: Explore And Apply, Volume 2 (2nd Edition)
Human Physiology: An Integrated Approach (8th Edition)
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