???? 120+ Challenge PAS 2 UnB ???? Hey, guys! This is Professor Matheus Aguiar from Física+ bringing you the first video of our 120+ Challenge ???? ???? Video Index: 00:00 Intro 0x:x0 Question x:x Question x:x Question ???? Important Links: PAS UnB Handouts: www.fisicamais.com/shop Instagram: www.instagram.com/aguiarprof ???? Did you like the video? So, like it, subscribe to the channel and share it with your friends to help strengthen our study community! Happy studying and let's go together towards approval! ????✨ #Desafio120+ #PASUnB #FísicaMais #UnB #aguiarprof #VestibularUnB #Física #Enem #pas2 Solved PAS UNB physics questions: PAS 2 UNB 2015 Human beings are subjected, on a daily basis, to sounds whose sound intensity varies from 1.0 × 10^(-12) W/m², called the audibility threshold, to 1.0 W/m², called the pain threshold. The comparison of sound intensities of different amplitudes is made using the decibel (dB). Using this unit, it is said that a sound wave of intensity IW/m² has 10 log (I/10^(-12)) dB, with the audibility threshold being used as a reference. Using the information above as a reference, assess the item and do what is requested in the item, which is type B. The sound intensity of the audibility threshold corresponds to a wave of 0 dB and that of the pain threshold, to a wave of 120 dB. Consider that an amplifier increases the intensity of a sound wave from IW/m² to I × 72 × 10^9 W/m². In this case, assuming that 0.301 and 0.477 are approximate values ​​for log 2 and log 3, respectively, calculate the amount of decibels that the amplifier adds to the original sound wave. After performing all the requested calculations, disregard, for marking in the Answer Booklet, the fractional part of the final result obtained, if any. PAS 2 UNB 2014 Waves are present in the simplest events, such as when a stone is thrown into a lake, when a musical instrument is played, and when a light bulb is turned on. Wave-like physical systems with fixed ends are characterized by their discretized movements and by forming stationary waves. Figure I illustrates this situation for a string of length d. Figure II sketches three examples of oscillating strings — y_i (i = 1, 2, and 3) — with fixed ends and amplitudes A_i, frequencies f_i, and wavelengths λ_i. The unit of length on the axes is the centimeter. Using this information as a reference and assuming 3.14 as the approximate value of π, judge the items and mark the correct option in the item, which is type C. The wavelength and frequency are sufficient to characterize a wave. In the excerpt “When the whistle from the textile factory hurts my ears, / I remember you”, by Noel Rosa, the use of the verb “to hurt” is associated with the speed and timbre of the sound waves in the aforementioned situation. Based on the data in Figure II, we conclude that a) A1 = A2 = A3. b) A1 A2 A3. c) f1 f2 f3. d) λ1 = 2λ2 = 4λ3. PAS 3 UNB 2014 The figure shows the outline of a cell phone signal transmission network. The network is composed of a receiving device (cell phone) and two transmission towers that emit identical electromagnetic waves, that is, with the same amplitude, with the same wavelength λ and in phase. The propagation medium of electromagnetic waves is homogeneous and isotropic. (...) Using this information as a reference, judge the item. If L_2 - L_1 = nλ, where n is a positive integer, then constructive interference will occur between the electromagnetic waves that arrive simultaneously at the receiving device. PAS 2 UNB 2014 Male crabs produce sound by touching their enlarged claws to various parts of their bodies or to the substrate on which they are located. The sounds produced in this way have been described as drumming, honking or whistling. Species-specific sounds have been identified in recordings at different frequencies and time intervals. For example, beach Chama-Maré crabs produce sounds between 600 Hz and 2,400 Hz, and mangrove chama-mares produce sounds between 300 Hz and 600 Hz. Internet: www.dosits.org (with adaptations). The figure below shows a diagram of a hypothetical situation in which a female mangrove crab hears the calls of two other mangrove crabs, one endemic to the beach and the other endemic to the mangrove. These calls interfere with each other and the speed of sound is 340 m/s. Regarding the sound perceived by the female mangrove crab, judge the following items. 18 If the amplitudes of the sound waves emitted by the male crabs are equal, then the resulting sound wave that reaches the female will have a frequency of 595 Hz and a beat frequency of 10 Hz. 19 The wavelength corresponding to the beat frequency is less than 0.29 m.