00:01
We have three different parts in which we'd like to write down some corresponding equations.
00:06
So our spring constant, k, is equal to mass times gravity divided by l.
00:14
So here we have 0 .5 times 9 .8 divided by 3 .920.
00:20
And let's plug that into a calculator.
00:22
0 .5 times 9 .8 divided by 0 .3920, and we get 12 .5 for a value for k.
00:32
Now, we also have x double prime plus k over m x is equal to zero.
00:39
So we get x double prime plus 12 .5 divided by 0 .5 x is equal to 0.
00:45
And so we get x double prime plus 25x equal to zero.
00:54
Now we also have a third expression.
00:57
We know omega is our square root of g over l, which is a square root of 9 .8 divided by 0 .3920.
01:06
So let's find our omega.
01:08
Our square root of 9 .8 divided by 0 .3920 is equal to 5.
01:15
Five radians per second.
01:18
So x of t is equal to, we have one cosine of 5t plus we have our value for our initial velocity, which is equal to point two.
01:38
So we have point two divided by five times sine of five t.
01:44
Or we can simplify this x of t is equal to cosine of 5t plus our point two divided by 5 which is 0 .04 sign of 5 t.
02:00
Now we have the similar things for b.
02:04
Now for b we have our mass of 0 .4 kilograms.
02:09
L is 1 .0889...