# Acceleration questions

#### LT72884

Why are there two formulas for acceleration?

A=Change of velocity/time
A=Force/Mass

Ok, now that thats out of the way, i need some light shed on a subject. If acceleration or gravity perse is 10m/s^2, how does this relate to distance.. Meters is a distance. So if an object falls 2 seconds, that is 20m/s^2 of acceleration. According to my book, how far an object falls is not the same as how fast.. If 9.8 is a constant, cant we treat it like velocity, such as, if i am driving at a velocity of 16.66m/s(60kmh) then in one hour i have gone 60km.

d=1/2(g)(t)^2 i know how to use the formula. haha. but why is acceleration measured in a unit of distance if it has nothing to do with distance.

I know that as soon as i drop a brick from a building, it takes a FULL second to reach that constant BUT as soon as it does reach that, isnt the distance the object falls at any given second after the first, going to be 10m/s? for example, i drop a brick off a dang building, between the third and fourth second, didnt it fall a distance of 10m/s because the constant was established after the first second and meters per second is a distance?

thanx

#### Doc Al

Mentor
Why are there two formulas for acceleration?

A=Change of velocity/time
A=Force/Mass
The first is the definition of acceleration; the second is Newton's 2nd law.

Ok, now that thats out of the way, i need some light shed on a subject. If acceleration or gravity perse is 10m/s^2, how does this relate to distance..
Given the acceleration, the initial velocity, and the time, you can compute the distance using basic kinematics.
Meters is a distance. So if an object falls 2 seconds, that is 20m/s^2 of acceleration.
No, the acceleration remains 10 m/s^2. After 2 seconds of falling the speed is 20 m/s (not m/s^2).

According to my book, how far an object falls is not the same as how fast.. If 9.8 is a constant, cant we treat it like velocity, such as, if i am driving at a velocity of 16.66m/s(60kmh) then in one hour i have gone 60km.
9.8 m/s^2 is a constant. But it's an acceleration, not a speed.

d=1/2(g)(t)^2 i know how to use the formula. haha. but why is acceleration measured in a unit of distance if it has nothing to do with distance.
Obviously it has something to do with distance--you just gave the formula for it! Acceleration is measured in units of distance over time squared (a speed per unit time).

I know that as soon as i drop a brick from a building, it takes a FULL second to reach that constant BUT as soon as it does reach that, isnt the distance the object falls at any given second after the first, going to be 10m/s? for example, i drop a brick off a dang building, between the third and fourth second, didnt it fall a distance of 10m/s because the constant was established after the first second and meters per second is a distance?
As soon as you drop the brick its acceleration is 10 m/s^2. After 1 second, its speed is 10 m/s. The speed--not the acceleration--takes a full second to reach 10 m/s. The acceleration is immediately 10 m/s^2.

To get the distance fallen between the 3rd and 4th second, use the formula for distance that you quoted.

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