Dynamics help: variable acceleration and angular velocity

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Homework Help Overview

The discussion revolves around two dynamics problems involving variable acceleration and angular velocity. The first problem involves a motorcycle accelerating along a curve, while the second problem pertains to a collar moving along a rotating rod. Participants are exploring the implications of the given conditions on speed and acceleration.

Discussion Character

  • Mixed

Approaches and Questions Raised

  • Participants discuss the application of kinematic equations to determine speed and acceleration. There is a debate about the appropriateness of using these equations given the variable nature of acceleration. Some participants question how to account for the curve's influence on acceleration.

Discussion Status

The discussion is active with participants offering different perspectives on the problems. Some guidance has been provided regarding the use of kinematic equations, but there is no consensus on the best approach to take, particularly regarding the relationship between acceleration and the curve.

Contextual Notes

Participants note the complexity of addressing two distinct problems in a single thread, which may lead to confusion in the discussion.

medynamics
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I have to do these 2 problems for homework, but I can't figure them out. Any help would be appreciated.

1. The motorcycle is traveling at 1m/s when it is at A(the origin). If the speed is then increased at \dot{V} = .1 m/s^2, determine its speed and acceleration at the instant t = 5 seconds. The motorcycle is following the curve y = 0.5 x^2.2. Rod OA rotates counterclockwise with a constant angular velocity of θ = 6 rad/s. Through mechanical means collar B moves along the rod with a speed of r = 4 t^2 m/s, where t is in seconds. If r = 0 when t = 0, determine the magnitudes of velocity and acceleration of the collar when t = 0.75 sec.

This is the link to the image for question 2:
http://s1308.beta.photobucket.com/user/jackcastle618/media/Dynamics4_zps5a431c20.jpg.html
 
Last edited:
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For question 1, start with the Kinematic Equations, specifically v = u + at
 
so using v = u + at:

v = 1m/s + .1(5)
v = 1.5 m/s

now I need a. i believe i need to find radial and tangential a?
so i have a = vdot
so a_r = .1 m/s^2
but how do I get the acceleration that is based on the curve y = .5x^2?
 
CaptainEvil said:
For question 1, start with the Kinematic Equations, specifically v = u + at
I don't think you can use that here. The rate of increase of speed is constant, but that's not the same as acceleration as strictly defined. Acceleration is a vector, or a component of a vector in a consistent direction.
medynamics, try to write down some equations relating dx/dt, dy/dt etc.

It's not a good idea to put two unrelated problems in the same thread.
 

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