Explaining Newton's three laws using masterpieces of painting. Part II

Best regards my Friends of steemit, some days ago I wrote a publication speaking about how we can use a masterpiece of painting to explain physical phenomena. We take the movement and Newton's three laws as a physical phenomena and the explanation of the third law was made with this idea (please see https://steemit.com/steemstem/@zambranoacosta/explaining-newton-s-three-laws-using-masterpieces-of-painting-part-i).

Today I bring the second post about how to explain newton's laws using master pieces of painting, this time we'll continue the disertation considering the first law or better known as law of inertia.

I'll explain the statement of 1st law in two parts, so let get started

First part of the statement of Newton's 1st law saids: "Every body will remain at rest unless external forces act on it to force these bodies out of that rest". In the Figure 1 we can see the masterpiece titled: "Still life with pottery" from Tomas Hiepes (1595 – 1674), we can see in the scene a bowl with fruits on a table, if we applied Newton's 3rd law we only have two forces acting on it: the weight of the body over the table (action, green arrow, applied down)and the force applied by the table over the body that we call normal force, acting in the opposite direction (reaction, orange arrow, applied up). We can see the bowl is in rest, is not moving, this is due to the cancellation of the force, because the algebraic sumatory of the forces acting over the body is equal to zero, in consecuense there is no movement.

Figure 1

In the Figure 2 we have the free-body diagram for this situation, showing the forces acting.

Figure 2

Notice, normal force is pointing up in the direction of the positive vertical axe, while the weight is pointing down in the direction of the negative vertical axe and both forces have the same intensity.

From this consideration we can write: Normal - weight = 0 (no movement).

Second part of the statement of Newton's 1st law saids: "A body moving with constant velocity, will be maintained with that movement unless on it act external forces that make it change the speed". In Figure 3 we see the masterpiece of Sibyl Kaufmann-Bezzola titled: "Flower sled courtship", where we se a couple of kids pulling a sled, the force of the kids (red and orange arrows) in principle they make the sledge move, however a certain time later the speed of movement of the sled is kept constant due to the friction force between the sled and the ground (grey arrow) which equals the forces of the children and annuls them. But the sled moves, it's true, but with constant velocity. The direction of the movement is indicated by the green arrow.

Figure 3

Finally in the figure 4 we have the free-body diagram for the sled, we see the force of the kid 1 (red arrow) and the force of the kid 2 (orange arrow) both pointing at the right side or positive horizontal axe, the forces add up in this side, so we can write: total positive force = force kid 1 + force kid 2. The friction force is pointing at the left side or negative horizontal axe and we can see that, the total positive force and the friction force have the same intensity, so we can write: total positive force - friction force = 0, I mean, we can say there are no movement but there is.

So I will left this open question: how is this possible? I will give the answer in the next post where Newton's 2nd law will bring light to this question.

It is important to highlight in Figures 3 and 4 there is present normal force (pointing up in the vertical possitive direction) and the weight (pointing down in the vertical negative direction), in those Figures I have focused in the explanation of the second part of the statement of Newton's 1st law, however strictly speaking these forces must be taken into account even if its sum is null.

Figure 4

Now we were able to explain 2 of 3 Newton's law using masterpieces of painting, so the question about if we can use masterpieces to explain physical phenomena is almost answered, and after to explain Newton's 2nd law we will ready to give a conclution about this good teaching tool.

This article is based on the article written by one of my best friend @augusto11julius titled CIENCIA Y ARTE: LA PINTURA VISTA DESDE LA PERSPECTIVA DE LA FÍSICA PARTES 1 Y 2 ( SCIENCE AND ART: PAINTING VIEWED FROM THE PERSPECTIVE OF PHYSICS PARTS 1 AND 2).

References:

1. Wagner L. Christian (2008) Luz, Arte y Física: la física en la pintura. Cádiz, España (Light, Art and Physics: the physics in the painting. Cádiz Spain)

2. Hewitt, Paul (1992) Concepts of physics.