How do I remember which formulas to use when studying 1-D Kinematics?
I know that I need x (position), v (velocity), and t (time), but I don't understand what x_o, V_x, V_xo, and A_x mean, or what formulas to use to find each one.
I know that I need x (position), v (velocity), and t (time), but I don't understand what
2 Answers
See below.
Explanation:
Generally used kinematic equations :
-
s_f=s_i+v_(is)Deltat+1/2a_s(Deltat)^2 -
v_(fs)=v_(is)+a_sDeltat -
v_(fs)^2=v_(is)^2+2a_sDeltas
Where:
s_f is the final positions_i is the initial positionDeltat is the time interval over which the motion occurred, whereDeltat=t_f-t_i Deltas is the change in position over the motion, whereDeltas=s_f-s_i v_i is the initial velocityv_f is the final velocitya_s is the acceleration of the object in the direction of the position you are measuring (i.e.a_y if you are looking at an object moving vertically ora_x if you are looking at an object moving horizontally)
Here it seems the preference of your teacher is to use
-
s=s_0+v_(0s)Deltat+1/2a_s(Deltat)^2 -
v_s=v_(0s)+a_sDeltat -
v_s^2=v_(0s)^2+2a_sDeltas
So, for you:
x_0 is the initialx positionV_x is the final or current horizontal orx velocityV_(x0) is the initial horizontal velocityA_x is the horizontal acceleration
Which equation you use will depend on which variable you are trying to solve for.
For example:
- If you're looking for the change in position but don't have time, you would use the third equation
- If you're looking for change in position and you do have time, but you don't know anything about the final velocity, you would use the first equation
etc.
I think a good technique would be to list all the factors you have in a horizontal row.
Explanation:
You fill in for each factor/variable the value and the units. One variable will be missing and one not mentioned at all in the data. Put a question mark beneath the factor you are told to find and a horizontal dash under the irrelevant one.
Each of the kinematic equations is missing one of the variables, look through them carefully and you'll see what I mean. This is how to decide which equation to use when you are starting out, with enough practice it does become obvious (promise!)