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Finding constant velocity,final velocity and acceleration of these cars?

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xod_s
#1
Oct26-11, 06:49 PM
P: 8
1. The problem statement, all variables and given/known data
Two cars go the same distance in a straight line. Car A covers the distance at a constant velocity. Car B starts from rest and maintains a constant acceleration. Both cars cover a distance of 517 m in 215 and are moving in the + direction. Whats the constant velocity of car A as well as the final velocity and acceleration of car B?

2. Relevant equations



3. The attempt at a solution
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PeterO
#2
Oct27-11, 06:02 AM
HW Helper
P: 2,316
Quote Quote by xod_s View Post
1. The problem statement, all variables and given/known data
Two cars go the same distance in a straight line. Car A covers the distance at a constant velocity. Car B starts from rest and maintains a constant acceleration. Both cars cover a distance of 517 m in 215 and are moving in the + direction. Whats the constant velocity of car A as well as the final velocity and acceleration of car B?

2. Relevant equations



3. The attempt at a solution
Did you by any chance mean 21 s [seconds] rather than 215 and no units.
xod_s
#3
Oct27-11, 02:07 PM
P: 8
@ PeterO "Did you by any chance mean 21 s [seconds] rather than 215 and no units."
Yes I did.Thank you for pointing that out.It's supoose to be 21 seconds not vaugely 215.Also if it helps I know for sure that the constant velocity of Car A is 2.40 m/s.

PeterO
#4
Oct27-11, 05:55 PM
HW Helper
P: 2,316
Finding constant velocity,final velocity and acceleration of these cars?

Quote Quote by xod_s View Post
@ PeterO "Did you by any chance mean 21 s [seconds] rather than 215 and no units."
Yes I did.Thank you for pointing that out.It's supoose to be 21 seconds not vaugely 215.Also if it helps I know for sure that the constant velocity of Car A is 2.40 m/s.
I hope you really meant 24.6 for the constant velocity.

One of the useful formulae for motion under constant acceleration is

s = (u + v)/2 .t

s = displacement, u = initial velocity, v = final velocity, t = time.

for acceleration zero, u = v so the (u + v)/2 = (v + v)/2 = v

The formula becomes s = vt, which you use to get that 24.6

when an object starts from rest, u = zero, so the formula becomes s = v/2 . t

from that you can get the final velocity.

as for acceleration .. the car reaches that velocity in 21 seconds, so you can divide by 21 to find the acceleration.


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