B Pre Lab Quiz Ans

MAE244

Introduction to Vibration

Pre-Lab Quiz - 1

Pre-Lab Quiz for Introduction to Vibration

Section ### : Name (Print): Student ID : 1. Briefly explain the following concepts: a. Natural frequency (2 point) The frequency of free vibration of a system without damping. Or the frequency at which an undamped system will oscillate upon momentary displacement from its rest position. b. Period (2 point) The interval taken to complete one cycle of vibration. c. Critical damping (2 point) The minimum damping that will prevent vibration happening for a system. 2. A mass-spring system has a frequency of 2 Hz. When the mass is decreased by 0.4 kg, the frequency is changed by 25%. Determine the mass m, and the spring constant k for the original system. (4 points) For original system, we have 1 k ---(1) f = 2π m Since the mass is decreased, so the system frequency will increase by 25%. That is, 1 k ---(2) 1.25 f = 2π m − 0.4 Now solve the above two equations with two unknowns, 1 m − 0.4 Using (1) / (2), , solve this to get m = 1.11kg. = 1.25 m Substitute m=1.11kg into equation (1), k can be calculated, k = 175.28 N / m