00:01
In this question, we have an airplane with a given mass, and it reaches a takeoff speed in 82 meters per second in 35 seconds.
00:12
And we're asked to calculate the thrust of the engines.
00:15
We can neglect air resistance, but not rolling friction.
00:20
So in order to do this question, we definitely need to use f9 equals ma, but we don't know acceleration.
00:29
So i think the first thing to try to calculate is the acceleration.
00:36
And of course we're given a final speed of 82 meters per second.
00:40
Presumably the airplane is starting from rest.
00:44
And we also know a time is 35 seconds.
00:48
So we can calculate acceleration here as just delta v over delta t.
00:54
The delta v is 82, this 82 minus zero.
01:00
And then the time is 35.
01:03
So if you place that into a calculator, you will get an acceleration of 2 .34 meters per second squared.
01:12
So now that we have the acceleration, we can do an f -net equation.
01:20
And in terms of a free body diagram, we know that the engines are going to be providing a thrust force forward.
01:28
So i'm going to label that as f -t.
01:30
And then there's going to be a rolling friction force pulling the plane back, kind of opposing the motion, i should say.
01:40
So the net force is going to be composed of ft minus ff...