Dynamics help: variable acceleration and angular velocity

Join the discussion
Ask a follow-up here, or get your own question answered by working scientists, mathematicians and engineers — people, not an autocomplete.
Real named experts · corrections over time · the nuance an AI answer skips
3 replies · 9K views
medynamics
Messages
4
Reaction score
0
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 [itex]\dot{V} = .1 m/s^2[/itex], determine its speed and acceleration at the instant t = 5 seconds. The motorcycle is following the curve [itex]y = 0.5 x^2[/itex].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 [itex]r = 4 t^2 m/s[/itex], 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:
Physics news on Phys.org
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.