00:01
So in this problem, we have a commuter train that's accelerating.
00:04
We have to figure out how much time it's going to take to accelerate to its top speed of 80 kilometers per hour with an acceleration of 1 .35 meters per second squared.
00:15
So the first thing we have to do is convert the 80 kilometers per hour top speed into meters per second.
00:20
We find that's 22 .2 meters per second.
00:23
Then we take the equation for acceleration, which is final velocity minus initial velocity divided by time.
00:29
And we rearrange it to solve for time.
00:32
So we find when we do that, that it's the final velocity minus the initial velocity divided by the acceleration.
00:38
So we take the top speed in meters per second, 22 .2.
00:42
We subtract the initial speed, which was zero, and then we divide by the acceleration of 1 .35, we see that it takes 16 .4 seconds.
00:52
The second question is asking about the deceleration.
00:55
So it's typical deceleration is negative 1 .65.
00:59
Meters per second squared negative because if the train is moving in a positive direction, it has to accelerate negatively to slow down...