00:01
Okay, so the context for this problem, we're talking about a woodpecker and its brain being protected from large accelerations by the skull and the tendons inside the skull.
00:10
So when it's pecking on a tree, its head comes to a stop after an initial velocity of 0 .6 meters per second, and it covers a distance of only two millimeters.
00:19
Find the acceleration both in meters per second squared and in multiples of g.
00:24
So we're given the initial velocity, we're told the head comes to rest, so the final velocity is zero, and the distance covered is two millimeters.
00:32
So we can go ahead and use the v final squared equals v naught squared plus two ad formula to find the acceleration.
00:41
Well, v final is zero, v initial is 0 .6, so 0 .6 squared plus, and then our distance is two millimeters.
00:51
Let's convert that to meters, 0 .002, times 2 .004d equals zero.
00:57
All right, 0 .6 squared is 0 .36, and 0 .36 divided by 0 .004 gives an acceleration of negative 90 meters per second squared, or if you want it in g's, that's approximately 9 .2 g's.
01:16
The negative is signifying that the head is slowing down, we're decelerating from the initial direction of velocity.
01:24
Okay, in order to find the stopping time, how long it takes to come to a complete stop, we'll have to use our full -on kinematics equation, where we know that our x is equal to our x naught plus vxt plus 1 .5 at squared...