A fishing boat weighing 147,150 N is towed by a much larger ship. The tow cable is linearly elastic and elongates 0.0278 m for each 1000 N of tension it carries. The viscous drag associated with pulling the fishing boat through the water can be assumed to be proportional to the velocity of the fishing boat, with 55,000 Ns/m being the constant of proportionality. At time t = 0, the large tow ship starts moving with constant velocity, V0 = 2 m/s. There is no initial slack in the cable. Required:
a. Propose a model of this system consisting of ideal lumped elements, that is, masses, springs, and dampers. Form a linear graph for your model, process that linear graph to create a normal tree, and on the basis of your normal tree, state the order of the system. Using the block diagram approach presented in class develop the transfer function relating speed of the towed boat to speed of the larger ship. Do this carefully, because the rest of the problem depends the accuracy of your model.
b. Based on outputs available from Part a) find an expression for the fishing boat displacement, x, as a function of time. Plot the displacement of both boats on the same graph.
c. What is the maximum force in the cable and at what time does it occur?
d. What is the elongation of the tow cable due to the drag of the fishing boat as → [infinity]?
e. It is desired to change the stiffness of the cable so that the fishing boat will approach the velocity of the tow ship as fast as possible without oscillating. What should the cable stiffness be in this case?

Infrared sensor is most used sensor in wireless technology where remote controlling functions and detection of surrounding objects/ obstacles are involved. this post will discuss about what is infrared sensor, its working principle, how it works, types, applications, advantages and disadvantages. what is infrared sensor

ir sensor is a simple electronic device which emits and detects ir radiation in order to find out certain objects/obstacles in its range. some of its features are heat and motion sensing.

ir sensors use infrared radiation of wavelength between 0.75 to 1000µm which falls between visible and microwave regions of electromagnetic spectrum. ir region is not visible to human eyes. infrared spectrum is categorized into three regions based on its wavelength i.e. near infrared, mid infrared, far infrared.

wavelength regions of infrared spectrum

near ir – 0.75µm to 3 µm
mid ir – 3 µm to 6 µm
far ir – > 6 µm
1 introduction to infrared sensor

fig. 1 – introduction to infrared sensor

working principle of infrared sensor

infrared sensors works on three fundamental physics laws:

planck’s radiation law: any object whose temperature is not equal to absolute zero (0 kelvin) emits radiation.
stephan boltzmann law: the total energy emitted at all wavelengths by a black body is related to the absolute temperature.
wein’s displacement law: objects of different temperature emit spectra that peak at different wavelengths that is inversely proportional to temperature.
key elements of infrared detection system

the key elements of infrared detection system are:

ir transmitter

ir transmitter acts as source for ir radiation. according to plank’s radiation law, every object is a source of ir radiation at temp t above 0 kelvin. in most cases black body radiators, tungsten lamps, silicon carbide, infrared lasers, leds of infrared wavelength are used as sources.

transmission medium

as the name suggests, transmission medium provides passage for the radiation to reach from ir transmitter to ir receiver. vacuum, atmosphere and optical fibers are used as medium.

ir receiver

generally ir receivers are photo diode and photo transistors. they are capable of detecting infrared radiation. hence ir receiver is also called as ir detector. variety of receivers are available based on wavelength, voltage and package.

ir transmitter and receivers are selected with matching parameters. some of deciding specifications of receivers are photosensitivity or responsivity, noise equivalent power and detectivity.