# Tag Info

1 vote

### Condition for 2 bodies to move together

Consider two bodies sliding past each other along a particular ramp direction. What is the possible relationship between the velocity vectors $\vec{v}_1$ and $\vec{v}_2$ ? Take the ramp and designate ...
• 33.8k

### Condition for 2 bodies to move together

your question is only a special case of constrained motion,in ur case it may be a wedge block system when there are motions along common normal,but when u talk about motion along x axis only normal ...
• 390
Accepted

### Acceleration of wedge and mass locked on axes

Using this algorithm you can solve almost all of high school mechanics(except rotational mechanics): I will ignore the wheel at the end of the rod since friction is negligible and therefore no ...
1 vote

### Why there are some the laws of phyiscs written for specific case?

It is written for a specific particle sometimes, but that's just a matter of language. Generally in physics if they write the law in singular ("a particle" rather than "any particle&...
• 4,446
Accepted

### Motion of a sphere at the end of a structure

Considering the kinematics of the situation, there are two cases possible: In the no-slip case, the velocity of the center is $v_C = \omega \, r$ and the contact point has no motion. The direction of ...
• 2,777

### Motion of a sphere at the end of a structure

The image shows only the initial position. The initial velocity is not shown in the picture and cannot be inferred from it. With the known laws of physics and both the initial position and initial ...
• 69.1k

### Are electric force and strong force equal in magnitude?

There is a repulsive force that comes into play whenever you try and confine particles to a restricted area. It is this repulsive force that stops the nucleus contracting to a point. Whenever you have ...
• 334k

### Vortex generated as a result of Newton's third law

What physical process is this claiming to describe? And what is the book and who are the authors? This does not resemble anything I've ever seen in physics; certainly not Newtonian Mechanics. I ...
• 2,883

### Catenary curved string with differing linear densities - Linear density distribution

The catenary equation can be derived by considering the minimization of the functionals, \begin{align} f[y]&=\int_0^{l_2}\mu gy\sqrt{1+\left(\frac{\mathrm dy}{\mathrm dx}\right)^2}\,\mathrm dx \...
• 24.7k
1 vote

### I don't understand how $F$ equals $ma$

Newton’s second law says that acceleration is proportional to Force. The proportionality constant is the mass. In a Newtonian context this is the definition of mass.
• 9,458

### I don't understand how $F$ equals $ma$

Think of it this way. You can do various things to an object to make it change its velocity. For example, you can push it, pull on it, put a magnet by it (if it is magnetic), drop it and so on. We ...
• 20.1k

### I don't understand how $F$ equals $ma$

So, we start with the assumption that a and m are directly proportional to F. That is not true. Besides not being an assumption, the statement should have been: Acceleration $a$ is proportional to ...
• 33.8k

### I don't understand how $F$ equals $ma$

@rayhan, So basically they say that Force is the derivative of momentum w.r.t. time (im sorry if you haven't yet studied basic calculus and cheers if you have), So F=dP/dt, and we can write it like , ...
1 vote

### I don't understand how $F$ equals $ma$

Essentially speaking, Newton's 2nd law states that the force applied by a body is equal to the rate of change of its momentum. Let's say the initial momentum of a body was $mv$, m being its mass and v ...

### I don't understand how $F$ equals $ma$

Mathematically Directly proportional means if you increase acceleration twice force will also increase two times and similarly for mass. So assuming mass m to be constant, $$F \propto a$$ Similarly, ...
• 335

### I don't understand how $F$ equals $ma$

Let F=mak, redefine a new quantity F'=F/k. There, now you have F'=ma. These ideas are mutually defined. Yes, in a metaphysical sense all we observe is some proportionality but when we sit down to ...

### Closest distance of approach

Rewrite the total energy as: $$H = C + \frac{1}{2}\mu v^2 + \frac{kq_1q_0}{r}\;, \qquad(1)$$ where $r$ is the relative distance, $v$ is the relative velocity, $\mu$ is the reduced mass, and $C$ is a ...
• 8,592
1 vote

### Closest distance of approach

Identical velocities implies zero relative velocity, meaning the objects are not moving with respect to each other - they are not getting any closer or farther from one another. Since the objects were ...
• 6,730

### Closest distance of approach

Say the two objects are moving to the right. As long as the one on the left is moving faster it gaining on the other and the the distance between them is decreasing. Once the one on the right is ...
• 7,539
1 vote

### What is physically going on when I stick my finger in a glass of water and the scale tips downards implying it got heavier?

At a macroscopic level there is a buoyancy upthrust acting on your finger, the reaction to which causes an increased force on the scale. At a microscopic level the effect is no different to putting a ...
• 20.1k

### What is physically going on when I stick my finger in a glass of water and the scale tips downards implying it got heavier?

I'm missing something here. There's some sort of subtlety I haven't gotten yet. Imagine the glass is not full of water but is full of air. A weightless piston can compress the air. It's completely ...
• 2,441
1 vote
Accepted

### Computing the maximum force a rod can bear

If you know ultimate tensile strength $T$ of material, then knowing breaking force of rod is trivial, $$F_{~br} = T \cdot A$$ ,where $A$ is rod cross-section area. However there is no way to compute ...
• 7,719
1 vote

### Computing the maximum force a rod can bear

Breaking stress is the maximum force that can be applied on a cross sectional area of a material in such a way that the material is unable to withstand any additional amount of stress before breaking. ...

### What is physically going on when I stick my finger in a glass of water and the scale tips downards implying it got heavier?

My take on this is that what you are experiencing is buoyancy. The your finger’s displacement of the water creates an upward buoyancy force on your finger. Since you are a stationary and relatively ...
• 9
1 vote
Accepted

### What is physically going on when I stick my finger in a glass of water and the scale tips downards implying it got heavier?

I'm not sure whether the previous answers address your interest in the molecular understanding of the change . The stress tensor tells us that pressure is momentum flux. The kinetic flux hasn't ...
• 1,032

### What is physically going on when I stick my finger in a glass of water and the scale tips downards implying it got heavier?

The scale tips because you are pushing down on it with your finger. It isn't as obvious that you are pushing on it as it would be if you touched the scale itself. You are pushing on the water, and the ...
• 27.8k

### What is physically going on when I stick my finger in a glass of water and the scale tips downards implying it got heavier?

By placing your finger in the water, you are exerting a force and the water responds to that force by rising higher in the glass. That force adds to the apparent weight of the water/glass system. If ...
• 5,630

### What is the action-reaction pair of static friction?

I am just giving anology for the problem. Frictional force arise due to surface roughness so both surface create frictional forces in action-reaction pair, surface1 for surface2 and vice versa. You ...
• 41

### Does the force between two magnetic poles ever reach zero?

The magnitude of the force between the two magnets will approach zero as they get further and further apart. It never (in theory) actually reaches zero because they are always a finite distance apart -...
• 35.6k
1 vote

### Does the force between two magnetic poles ever reach zero?

Like gravity or electrostatic attraction, magnetism reduces with distance. However, while the first 2 have an inverse square law (the force diminishes with the square of the distance), the magnetic ...
• 9,854

### Bottom point being at rest in pure rolling

But since this makes the bottom point at rest,then what causes that point to rotate again with the disc? Even though it is instantaneously at rest there are still forces acting on it. There is it’s ...
• 69.1k
1 vote

### Can the wavelength of the standing wave be different from the wavelength of the sound it emits?

This might surprise you, but the wavelength of the standing wave in a string is pretty much always different from the wavelength of the sound it emits. What is equivalent between the two vibrations ...

• 7,719

### Why is Tangential Speed unaffected by a change in Centripetal Force?

When you move your hand you move the center of the circle so the motion is not purely circular anymore. The tension in the string will have a component tangent to the instantaneous trajectory. The ...
• 6,815
1 vote

### Why is Tangential Speed unaffected by a change in Centripetal Force?

If we make an object move faster along the same circular path, we must apply a tangential force component to give it a tangential acceleration. But because the object is moving faster it has to be ...
• 28.3k

### What is the gravitational force acting on a massless body?

In classical physics you have an indeterminacy of the type $$a=\frac{GM}{r^2} \frac{0}{0} \tag{1}$$ This means that unless you have some new information to find that limit you cannot proceed. However, ...
• 2,143
1 vote

### What is the gravitational force acting on a massless body?

Even in Newtonian physics it is possible to see that a massless particle may undergo an acceleration. The problem is ill-defined because whilst the force between a massive and a massless particle is ...
• 113k
Ol' Isaac Newton goofed. He wrote: $F = \frac {G M_1 M_2}{d^2}$ when he should have written: $F = \frac {G E_1 E_2}{d^2}$ (with a different value and units for G) where it is to be understood that $E$ ...