1. Sep 29, 2011

### LanaStClair

Hello, I'm in 8th grade advanced Science, we just started physics but I'm very confused. Can anybody help me on how to calculate acceleration and magnitude? Thanks This is NOT homework, I am just trying to study for an exam tomorrow.

Last edited: Sep 29, 2011
2. Sep 29, 2011

### spacelike

Well magnitude is a general property of vectors. Not just acceleration.
For example. velocity is a vector, the difference between "velocity" and "speed" is that "velocity" has a magnitude and a direction, whereas "speed" only has magnitude.

So "magnitude" is like the length of the vector. Another way to look at is is that if you are doing 1-dimensional problems (which you probably are) then your "vectors" are basically just a single number that can be positive or negative, then "magnitude" is like the absolute value.

As for acceleration, just think of it as the change in velocity over time.
$$a=\frac{\Delta v}{\Delta t}=\frac{v_{f}-v_{i}}{\Delta t}$$

3. Sep 29, 2011

### GrantB

Hello :)

Acceleration is a rate of change of velocity, where velocity is a rate of change of position.

If I run in a 100m race, and finish in 10 seconds, my velocity is how fast I go from beginning to end. In this case it is:

$v = \frac{finish-start}{time} = 10m/s$

In this case, the start is the x=0 position, and finish is the x=100 position.

Acceleration is similar to this.

If I start by going 5m/s and end at 15m/s, then my acceleration is:

$a = \frac{final velocity - initial velocity}{time} = \frac{15m/s-5m/s}{10s} = 1m/s^2$

Now, all of these are averages for the given example, and I randomly chose numbers.

Also, these are all magnitudes. If I were to attach a direction to the magnitude, it would become a vector.

Hope this helps.

4. Sep 30, 2011