Thread: Acceleration calculation - what am I doing wrong?

1. Acceleration calculation - what am I doing wrong?

I am trying to figure out how to use the formula for calculating acceleration.

First try:
Initial speed - 0 metres/s^2
Final speed - 100 metres/s^2
Time - 10 seconds.
Follow up question: How many g's is 10 meters/s^2?
Answer is 10 meters/s^2/9.8 meters/s^2= 1.0204 g's.

Second try:
Initial speed - 0 metres/s^2
Final speed - 1,000,000 metres/s^2 (1,000 KM)
Time - 1000 seconds.
Follow up question: How many g's is 1000 meters/s^2?
Answer is 1000 meters/s^2/s^2/9.8 meters/s^2 =102.04 g's.

Am I doing this correctly?

2. Established Member
Join Date
Jan 2002
Posts
922
appears to be correct Solfe...
Rememebr to always start with the formula and simply plug in the knowns and solve for the unknown.

V(f) - V(i) = at
100 m/sec - 0 = (a)(10 sec)
Now solve for a.

3. Originally Posted by Solfe

Final speed - 100 metres/s^2

::snip::

Am I doing this correctly?
Maybe it's the speed in metres/s^2 instead of metres/s

4. Originally Posted by grapes
Maybe it's the speed in metres/s^2 instead of metres/s
I was doing this on paper, so I think you are right. I was writing the wrong terms.

I will get the hang of this someday.

5. Originally Posted by Solfe
I am trying to figure out how to use the formula for calculating acceleration.

First try:
Initial speed - 0 metres/s^2
Final speed - 100 metres/s^2
Time - 10 seconds.
Follow up question: How many g's is 10 meters/s^2?
Answer is 10 meters/s^2/9.8 meters/s^2= 1.0204 g's.

Second try:
Initial speed - 0 metres/s^2
Final speed - 1,000,000 metres/s^2 (1,000 KM)
Time - 1000 seconds.
Follow up question: How many g's is 1000 meters/s^2?
Answer is 1000 meters/s^2/s^2/9.8 meters/s^2 =102.04 g's.

Am I doing this correctly?
Hello Solfe,

there's a wrong unit in your initial variables:

#1 Speed (i.e. velocity) is expressed in distance per time. E.g Miles per hour or metres per second (m/s). Accelerations, i.e. change of velocity over time, is therefore expressed as distance per times squared: (m/s^2)
#2 As acceleration is change of velocity over time one can write: a = v/t. Solving for v this yields : v = a*t. So simply multiply your acceleration with time and you'll get your final speed.

Ex

P.S.
A more general equation is a = ^v/^t. Acceleration equals change of velocity in a certain tie period. Therefore: a = (v2-v1)/(t2-t1)

6. Or in distance terms v^2 = u^2 + 2.a.s where a is acceleration and s distance in consistent units. u is the starting speed.
the link from distance to time is s= u.t + 1/2. a.t^2

7. Established Member
Join Date
Apr 2004
Posts
1,801
FYI, you are dealing with constant accelerations. Whilst motion under gravity tends to have constant acceleration, mechanical devices like cars tend not to have constand accelrations.

So a sports car that does 0-60mph in 5 seconds has a average acceleration of about 12mph per second (a rather mixed unit, but it helps understand the principle), in practice its accleration will not be constant, and the distance it travels will not be precisely half-a-t-squared.

Posting Permissions

• You may not post new threads
• You may not post replies
• You may not post attachments
• You may not edit your posts
•
here