# Tag Info

Accepted

### Why is the shape of a hanging chain not a "V"?

The V shape makes sense for an ideal chain with all of its mass concentrated at the midpoint (with the rest of the chain being massless). But now consider a chain with its mass distributed over 3 ...
• 12.4k

### Why is the shape of a hanging chain not a "V"?

Sorry to put in my contribution so late in the proceedings, but I don't think anyone has yet presented this simple argument based on forces… Suppose the chain did hang in a V shape. Consider a small ...
• 36.3k

### Why is the shape of a hanging chain not a "V"?

The V has a higher gravitational potential energy than the catenary does. To see this, consider pulling down at the center of the catenary very hard. As you pull down, the chain deforms into a V. But ...
• 104k
Accepted

### Why are arched bridges stronger than flat bridges?

Fracture happens under tension - that is, when you pull on something hard enough, it rips. The key to understanding the arc design hinges on understanding that it lowers the maximum tensile force. ...
• 119k

### Plank overhanging off a building — where does the normal force go?

Adding to Chemomechanics' answer, the resulting forces is dependent also on the plank's geometry and material. Here's the behaviour of a particular material and geometry of a plank. Fine, it's ...
• 506
Accepted

### Hanging a hammer from a table and a stick so that its midpoint is outside of the support of the table

The ruler is actually being supported by the handle of the hammer to provide two points of support so the downward force from the string lies between the two and the system balances. Moment on the ...
• 2,234
Accepted

### Why does the curve of a hanging chain not minimize the area below it?

What is wrong with your argument is this paragraph: If we imagine the chain as having many small segments, then the potential energy of each segment is $E_p=mgh$. As the number of small segments ...
• 13.7k

### Why does the curve of a hanging chain not minimize the area below it?

To put the accepted answer in mathematical terms, if you have a curve $y(x)$, hanging fixed at $x_0$ and $x_L$ at an height $h=y(x_0)=y(x_L)$, of total length $L$ and mass $M$ then then linear mass ...
• 4,799

### Hanging a hammer from a table and a stick so that its midpoint is outside of the support of the table

You can make two free body diagrams. One for the plank (with pink arrows), and one for the hammer (with blue arrows). Then examine if the forces can balance out. The reaction force on the plank from ...
• 38.9k
Accepted

### What holds up the lowest point of a rope following a catenary curve?

That lowest point is not exactly horizontally aligned with the neighboring points. It is slightly below. If it wasn't, then, as you describe, there would be a net vertical force downwards. If that ...
• 51.7k
Accepted

### Plank overhanging off a building — where does the normal force go?

Of the existing answers, one suggests that the reaction force can be represented by two forces, whereas the other says that the force is a distributed force. These aren't incorrect, but they aren't ...

• 38.9k

### Hanging a hammer from a table and a stick so that its midpoint is outside of the support of the table

When you use an object to strike another object, there is a place called the "center of percussion" where you don't get a "sting" in your hand. This is sometimes called the "sweet spot" in sports (...
• 119k

### Why the dust on the wing cannot be cleaned by air flow?

There are two factors at play here: Static electricity causes dust to adhere to the wings of a plane. When a plane is in the air, there is nowhere to dissipate static charge buildup (as that usually ...
• 35.7k