# Tag Info

Accepted

### Why does a charge need to have a velocity to experience force in a magnetic field?

The question "why?" in Physics may have different answers, depending on the depth one wants and is able to dig. Lorentz force and the development of special relativity So, assuming you know ...
• 9,521

### How does a snake climb the wall?

You might be picturing the whole thing wrong. The walls are not smooth in the real world. Normal reaction has a vertical component, and the weight of the snake is balanced by this. ---- Snake ...
• 12.3k
Accepted

### How does this tensegrity table work?

Stable mechanical equilibrium broadly means that any movement would incur a net energy penalty. This is intuitive when we see a ball at rest in a dip, for example; itâ€™s clear that any rolling would ...
• 26.4k
Accepted

### Weightlessness at the highest point of a vertical circular motion

It's easiest to see what is happening if one looks at the object from the perspective of an outside observer: What keeps the mass from falling down, at its highest point? Nothing. Nothing keeps the ...
• 49.9k

### How does a snake climb the wall?

The answers vary tremendously by species, but speaking from experience, a sufficiently wet young snake can use the surface tension of the water on their body to pull them to the surface they are ...
• 49.9k

### Weightlessness at the highest point of a vertical circular motion

Perhaps you mean weightlessness in the title? The mass of an object does not change as it follows a trajectory. Suppose you throw the mass. If follows a curved trajectory. When it reaches the peak, ...
• 40k

### A person is pushed forward in a bus when brakes are out because of inertia or pseudoforce?

Yes, that is just two ways of saying the same thing. The different descriptions stem from using different reference frames. The pseudo force (I prefer the term "inertial force") is simply ...
• 102k
Accepted

### Why are forces superimposable in Classical Mechanics? Does this also apply in higher theories like General Relativity and Quantum Mechanics?

Since Newton's laws are treated as axioms in classical mechanics and the forces act linearly in the second Newton's law, from that perspective, it is axiomatic that forces are additive. But of course, ...

### How does this tensegrity table work?

What's confusing here is probably that the lifting is dose via the tensile force of the rubber band, which due to the placement on the arms pulls down the bottom and up the top part. Mechanically, ...
• 4,397

### How does a snake climb the wall?

Principally it is due to surface tension (not friction force). Googling something like surface tension insects wall would produce many hit of different level of difficulty (in terms of knowing physics....
• 59.4k

### Why does a charge need to have a velocity to experience force in a magnetic field?

If there is a field force, then it can do work on a particle that is being affected by the field. Therefore, the energy corresponding to the work done is stored or removed from the field between the ...
• 399

### Weightlessness at the highest point of a vertical circular motion

At the highest point, the mass doesn't fall because the centripetal force required for circular motion ($mv^2/r$) is exactly provided by the weight of the mass ($mg$). The tension in the rope is zero ...
• 206
Accepted

### Should a box on a surface have an even number of forces?

When you do a free body diagram, you should focus only on forces and moments acting on the system of your interest. As an example, if you're studying the equilibrium of the box, you should only draw ...
• 9,521
Accepted

### What happens when we apply the exact same pulling force as bonding force of glue?

Your problem may seem as a genuine mechanics problem at first, but it's not. We could formulate it in equivalent ways, such as "what happens if a tub can only be filled with 20 litres of water, ...
• 1,541
Accepted

### Infinite force paradox in pulling a car out of mud

All the equation $$T = \frac{F l}{2d}$$ is telling you, is that you require a infinite tension in the rope to make sure that a non-zero force applied to it results in zero deflection. If the ...
• 5,191
Accepted

### Aren't there only 3 fundamental forces?

Regardless of the underlying mechanisms, gravity provides a channel for an object to realize the presence of other objects around. In other words, it mediates an $interaction$, one way or another. So ...
• 3,772

### A person is pushed forward in a bus when brakes are out because of inertia or pseudoforce?

Be careful because there is an illusion taking place here. When the bus brakes, then the person is not being pushed forwards. Rather, the bus is being pulled backwards by a friction force - the person ...
• 51.3k

### Where is the reaction force $F_2$ of $F_1$ applied?

Whenever in doubt, think fundamentally at a basic level. Clearly define the system that you are applying forces on. Case 1: Here the force on the escaping gas is applied by System 2. So, if system 2 ...
• 399

### Does a rubber mat reduce the impact to the floor below?

If dropped, the falling barbell will carry a considerable amount of kinetic energy when it hits the floor. Preventing damage to the floor involves managing that impact energy. Here is how to do it: A ...
• 94.5k

In a simplified model such at drag being proportional to the speed $v$ or the squared speed $v^2$ the speed never reaches terminal velocity in general. Rather, it approaches the terminal velocity as $... • 57k 3 votes Accepted ### Pauli exclusion principle and van der Waals force Do intermolecular forces due to Pauli exclusion happen in reality? Yes. Despite the fact that repulsive electromagnetic forces alone are more than enough to stop us from making a neutron star, Pauli ... • 8,022 3 votes ### Infinite force paradox in pulling a car out of mud Getting a good equation in physics always involves some simplifying assumptions. When you see infinities, the first thing to do is to check your simplifying assumptions and see if they still hold. The ... • 102k 3 votes ### Infinite force paradox in pulling a car out of mud You can never have$d=0$in real life because every rope is elastic and as soon as you start to apply a force on it it will deflect causing$d>0$Applying equations in Physics always involves a ... • 3,180 3 votes ### What are internal and external forces? First you have to decide what is and isn't part of your "system". Let's say I have a bunch of masses orbiting each other. These will exert forces on each other - internal forces - and total ... • 111 3 votes ### What are internal and external forces? You define a system. Any internal forces within the system will be Newton Third Law pairs, ie for every internal force on part of system A due to part of system B there will be another internal force ... • 97.1k 3 votes ### Is the gravitational potential energy of an object on the ground 0? Gravitational potential energy only makes sense relative to two points and you can set any one point to any potential you want since only differences in potential energy matter. So you can call ... • 2,728 3 votes ### Why does the block move if the net force is zero? The block is not pulling in the free-hanging rope with$5\,\mathrm N$. It is pulling with much less force. That the rope "follows the motion" of the block as the block is pushed, does not ... • 51.3k 2 votes ### What is the point of torque? Yes, you can consider torque as a mathematical trick, to find the angular acceleration. In fact, you cannot easily find the acceleration by taking dm masses, especially if the body is rotating about ... • 399 2 votes ### How does$g\$-force work?

"G-Force" is a colloquial term. However, it is indeed a very common one. G-forces show up most commonly in systems where one is constrained to accelerate at a certain rate (although you ...
• 49.9k