00:02
Okay, so this question is actually about the frictions.
00:10
So in order to solve the problem, first we need to know how to calculate the friction.
00:17
And this is called the friction law, right? we know the friction between two objects.
00:29
In this case, it's between the objects and the ground, is actually equal to the friction coefficients.
00:40
Times, right, the force between the objects, between two objects.
00:55
Here, in this case, is between the object and the ground, right? so now we can use this to analyze.
01:09
Before we do an analysis, right, we need to make sure to know that this coefficient is constant, right, between two objects, no matter of what kind of force you apply, it remains constant.
01:26
So in order to compare the magnitude of the friction, what we need to compare here is just the force, the interaction between the objects and the ground.
01:45
So now we can start to do the analysis.
01:49
In the case a, we say the force, you applied on the objects is totally parallel to the ground.
02:01
So the interaction between the object and the ground here should actually equal to the gravity of the objects.
02:22
And in the b case, we find that the interaction, of course, the object was due to feel the force of the gravity.
02:36
But at the same time, you find because the force applied has a angle, right, is now not parallel to the ground.
02:46
So we can do a decompose of the force.
02:49
And what you'll find is that you'll find a vertical component of that force.
03:03
Which means the total force that the object received in the vertical direction, right, is equal to the gravity, right, minus the vertical component of the f, because they have the totally opposite directions, right? so this magnitude, right, also equal to the interaction, right, the force between the objects and the ground, because in the vertical direction, it's not moving, right? it's vertical in vertical direction.
03:52
It's in equilibrium, right? it's balanced...