00:01
We are looking to find the acceleration of an elevator, which has a mass of 637 kilograms, and a tension force pulling it up of 8 ,000 newtons.
00:11
So let's look at a free body diagram.
00:13
We have force of gravity going down, and normal force going up.
00:17
Pretend that is a straight line.
00:19
So, excuse me, not normal force.
00:21
This is tension force this time.
00:22
So our equation is net force in the vertical is equal to mass times acceleration.
00:28
So we have tension minus force of gravity is equal to mass times acceleration.
00:34
And we're looking for acceleration.
00:36
So simply divide both sides by mass.
00:40
And so that's our equation.
00:41
Tension minus force of gravity, which we know is really mass times gravity.
00:45
So we can plug that equation in divided by mass.
00:49
So let's plug in our values.
00:51
We have acceleration is equal to 8 ,000 minus mass times gravity.
01:01
All divided by 637.
01:04
And when we do that, we get 3 .35.
01:08
Wrong problem, excuse me, 2 .76 meters per second squared.
01:16
And it's positive, which tells us it's going in the upward direction.
01:21
Now this second question, that was a little bit harder because it has a ramp, but it's not too bad because we're told it's frictionless.
01:28
And it has an angle of 20 degrees.
01:30
So let's draw a free body diagram.
01:31
Here's my object.
01:32
Going directly down is force of gravity.
01:35
And going perpendicular to the surface is normal force.
01:38
And so remember when you're doing ramps, it is beneficial to change your axis to where your axis is right here on the ramp.
01:45
So let's redraw that.
01:46
So here is my ramp, which is my axis.
01:49
Here's my object...