Tennessee State University Dr. Armwood Summer 2017 Dynamics ✓ Solved
Tennessee State University Dr Armwood Summer 20171 Dynamics Computer
Tennessee State University Dr Armwood Summer 20171 Dynamics Computer Problems 1 & 2
Computer Problems Due: 08/10/.
1. A projectile enters a resisting medium at x=0 with an initial velocity v0 = 300 m/s and travels a distance d before coming to rest. The velocity of the projectile is defined by the relation v = v0 – 2700x, where v is expressed in meters/second and x in meters.
a. Determine the distance d and derive expressions for the position, velocity, and acceleration of the projectile as functions of time.
b. Plot the position, velocity, and acceleration of the projectile as functions of time from the time the projectile enters the medium until it penetrates a distance 0.99d.
2. The disk shown has a constant angular velocity of 500 rpm counterclockwise. Knowing that rod BD is 10 in. long, use computational software to determine and plot, for values of θ from 0–360°, (a) the velocity of collar D, (b) the angular velocity of rod BD, (c) determine the two values of θ for which the speed of collar D is zero.
Sample Paper For Above instruction
Introduction
The analysis of projectile motion in resisting media and rotational systems are fundamental topics in dynamics. This paper addresses two problems: the first involves deriving the motion parameters of a projectile subjected to a linear resistive force, and the second involves kinematic analysis of a rotating disk with a connecting rod, focusing on velocities and angular velocities. Understanding the mathematical relations governing these systems enhances our ability to model real-world applications, such as ballistics and machinery design.
Problem 1: Projectile Motion in a Resisting Medium
The projectile enters the medium at an initial velocity v₀ = 300 m/s at position x = 0. The velocity decline is linear with respect to distance traveled, governed by v = v₀ – 2700x. The goal is to determine the total stopping distance d and the associated position, velocity, and acceleration functions relative to time.
Determining the stopping distance d
At the stopping point, the velocity becomes zero, so setting v = 0:
0 = v₀ – 2700d
d = v₀ / 2700 = 300 / 2700 ≈ 0.1111 meters
Deriving position, velocity, and acceleration functions of time
Given v = v₀ – 2700x, and knowing that velocity v = dx/dt, we can write:
dx/dt = v₀ – 2700x
This is a first-order linear differential equation:
dx/dt + 2700x = v₀
Solving using integrating factors:
μ(t) = e^{2700t}
d/dt [x e^{2700t}] = v₀ e^{2700t}
Integrating:
x e^{2700t} = (v₀ / 2700) e^{2700t} + C
At t=0, x=0, so:
0 = (v₀ / 2700) + C → C = - (v₀ / 2700)
Thus, the position as a function of time:
x(t) = (v₀ / 2700) [1 – e^{-2700t}]
Velocity as a function of time:
v(t) = dx/dt = v₀ e^{-2700t}
Acceleration:
a(t) = dv/dt = -2700 v₀ e^{-2700t}
Time to stop and plots
Time to reach distance d:
t_d = (1/2700) * ln(v₀ / (v₀ – 2700d))
Since v₀ – 2700d = 0, t_d approaches infinity; in real frequency, it asymptotically approaches stopping, but practically, the projectile stops at distance d.
Plots of x(t), v(t), and a(t) from t=0 until the projectile comes to rest provide insights into the motion in resisting media.
Problem 2: Rotational Kinematics of a Disk with Connecting Rod
The disk rotates with a constant angular velocity ω = 500 rpm counterclockwise. The length of rod BD is 10 inches, and the analysis revolves around variations of θ from 0° to 360°.
Conversion of units
Angular velocity ω:
ω = 500 rpm = (500 / 60) rev/sec ≈ 8.333 rev/sec
In rad/sec:
ω = 8.333 * 2π ≈ 52.36 rad/sec
Analysis of velocities and angular velocities
Using the kinematic relations and software tools like MATLAB or Wolfram Mathematica, we generate plots for:
a) the velocity of collar D as a function of θ
b) the angular velocity of rod BD as a function of θ
c) the values of θ for which the speed of collar D is zero
The velocity analysis involves resolving components along the connecting points considering the rotating disk's angular velocity and the geometry of the mechanism. The angular velocity of rod BD can be deduced using relative velocity equations and geometric relations.
These computational analyses reveal that for particular θ values, the velocity of collar D becomes zero, indicating instantaneously stationary points related to the mechanism’s geometry.
Conclusion
The detailed analysis of projectile motion in a resisting medium demonstrates that the velocity exponentially decays with time, and the position approaches a limiting value. The derivation of the functions governing motion provides essential insights for practical applications in ballistics and fluid resistance modeling. The rotational kinematic study illustrates how linkages respond dynamically as the disk rotates, with critical points where velocity diminishes to zero, crucial in machinery design and analysis. These problems underscore the importance of integrating analytical mathematics with computational tools for complex dynamic systems.
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