Expert: James J. Kovalcin - 11/7/2009

Question
can you please give me all the formulas for the 9th grade? and it should be about speed, time and distance. can you please explain when do when do we use them when solving a problem.


Answer
First of all there is no such thing as "all the formulas for the 9th grade"!
However, if you a asking specifically about the relationships among distance, velocity, acceleration and time, there are two:
Df=1/2*a*t^2+Vo*t+Do  and Vf=a*t+Vo
Where: Do is the position of the object aat the beginning of the problem
Df is the position of the object at the end of the problem
Vo is the velocity of the object at the beginning of the problem
Vf is the velocity of the object at the end of the problem
a is the rate at which the velocity is changing [the acceleration]
t is the time between the beginning and end of the problem
Since there are 6 distinct variables and two equations, any time that you can identify 4 of the 6 variables you can always solve for the other 2!