home > q&a board > mechanical engineering > topic: urgent11.41

Q BgQuestion:

Scholar
Karma Points: 200
Respect (83%):
posted by  ale_g_20 on 7/14/2008 4:50:46 PM  |  status: Live  

urgent11.41

Course Textbook Chapter Problem
Classical Mechanics Vector Mechanics for Engineers: Dynamics (8th) by Johnston, Beer, Clausen 11 N/A
Question Details:
Can you solve this problem please. I dont understand it! problem # 11.41
automobile A starts from O and accelerates at the constant rate of 0.75 m/s2.  A short time later it is passed by bus B which is traveling in the opposite direction at a constant speed of 6 m/s. Knowing that bus B passes point O 20 seconds after automobile A started from there, determine when and where the vehicles passed each other.
Bonus Point Alert! Earn +4 additional karma points for helping this annual member.

AAnswers:

Answer Question
Expert
Karma Points: 1,040
posted by rooya on 7/19/2008 12:16:45 PM  |  status: Live
Asker's Rating: Lifesaver   
Response Details:
Given
aA=0.75
VB=6
but it is given that bus reaches point O in 20sec
Distance travelled by bus B in 20s
D=VB*t=6*20=120
 
Let t be the time taken when A&B meet
Distance travelled by A
we know that
S=Ut+at^2/2
x=0+1/2*0.75*t^2
x=0.375t^2 ------------(1)
but Distance travelled by B
(120-x)=VB*t------------------(2)
x=120-6t
from 1&2
120-6t=0.375t^2
t=11.6 s
from 1
x=50.46 m
 
Answer Question
Ask New Question

Join Cramster's Community

Cramster.com brings together students, educators and subject enthusiasts in an online study community. With around-the-clock expert help and a community of over 100,000 knowledgeable members, you can find the help you need, whenever you need it. Join for free today » How Cramster is different than tutoring »

Need Help In

Useful Links