00:01
The first step to solving this problem is to find the acceleration of the elevator.
00:05
So when we look at what's happening with the elevator, we have two forces moving up and one force moving down.
00:12
We've going to have the tension force from the counterweight and the tension force from this motor.
00:18
And the masses of the elevator are 500 kilograms.
00:22
The counterweight is 150 kilograms.
00:25
And we are told that the final speed that the elevator reaches is 10 meters per second.
00:30
After it travels a distance of 40 meters.
00:33
And so to start with, we need to find the acceleration.
00:37
We can do that using kinematics.
00:39
We know that the initial speed is going to be zero.
00:43
So we can use our time -independent kinematic equation, solve it for acceleration, plug in our values for the final velocity.
00:50
Initial velocity is zero, and the change in position is 40 meters.
00:55
And we get an acceleration of 1 .25 meters per second.
01:00
Once we know the acceleration, we can then evaluate this as a sum of the forces on the elevator and counterweight.
01:07
So the elevator, it's mass times acceleration.
01:11
It's net force.
01:13
It's going to be equal to the two tension forces up.
01:17
So tension one is from the counterweight.
01:19
Tension two is from the motor force.
01:21
And then that it's going to subtract the weight force down.
01:26
For the counterweight, it's net force...