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. How long does it take for the door to close after it is opened? a. 11 s b. 8 s c. 5.5 s d. 3 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. How long does it take for the door to close after it is opened? a. 11 s b. 8 s c. 5.5 s d. 3 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.
How long does it take for the door to close after it is opened?
Close-up view
etermine;
The volume of the object given that the initial level of water in the measuring cylinder
23cm3.
The density of the object.
simple cell made by dipping copper and zinc plates into dilute sulfuric acid solution. A bull
onnected across the plates using a wire.
State what constitute current flow through the wire
The bulb connected across is observed to light for some time and then goes out. State t
possible
asons for this observation.
State two ways in which the processes named in question (b) above can be minimized t
the bulb light for a longer period.
ead
is rated 80Ah. Determine the current that can be drawn continuously
Answers with -1.828, -1.31 or 939.3 are not correct.
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.
Chapter 2 Solutions
College Physics: Explore And Apply, Volume 2 (2nd Edition)
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