This tag is for the classical concept of forces, i.e. the quantities causing an acceleration of a body. It expands to the strong/electroweak force only insofar as they act comparable to ‘classical’ forces. Use [tag:particle-physics] for decay channels due to forces and [tag:newtonian-mechanics] or ...

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2
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2answers
528 views

Average Force vs Net Force

The F in $$Impulse = F*t$$ is said to be the average force. For a ball dropped vertically onto a horizontal surface, the average force, F, on the ball from the floor is: $$F = \frac{\Delta{p}}{t}$$ ...
2
votes
2answers
20 views

Glass tube diameter to hold water when turned upside down

If I have a glass tube that is closed at one end and has length l, how can I find the range of diameters that the tube must be so that the water does not fall out of the tube when the tube is turned ...
1
vote
1answer
20 views

Does a capacitor experience a Newtonian reaction when being charged?

Say I have a capacitor that is being charged with a battery. There are two wires, one on the positive and one on negative terminal of the battery which go to a capacitor. During the charging, a ...
0
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1answer
221 views

Question on Binet's equation

Is there a difference in Binet's equation when the force acting on a body is attractive and repulsive? I mean, if the force has a magnitude $F(r)$, is it Binet's equation always ...
5
votes
1answer
182 views

How do I describe and calculate the effect of an impacting object?

My lab studies the physiology of impact injury on biological tissues. I use a pneumatic cylinder to impart injury into a biological sample and then assess the molecular and physiological changes in ...
-3
votes
0answers
20 views

Calculating fields of two magnets

I want to use two NEODYMIUM IRON BORON permanent magnets to create a repulsion between them. In which one PM is attached to the robot (which has three wheels and its weight is 5KG) and the another PM ...
1
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4answers
69 views

Negative friction force, positive normal force

I realize that formulas don't always tell the whole story, but there seems to be some information missing from the equation: $F_f=\mu F_N$ Imagine we say up and right is positive. Then if an object ...
1
vote
0answers
40 views

How does the gradient operator pick up a minus sign when the reference frame is switched from one particle to another? [on hold]

A potential between two particles, $i$ and $j$, is given as a function only of the separation distance, $$V_{ij} = V_{ij}(|r_i − r_j|)$$ It should follow that the force by $j$ on $i$ is equal and ...
1
vote
1answer
147 views

Can two bodies of different mass attached at ends of string passed over a frictionless pulley produce equal tension on both sides?

In my textbook there is given a case that to calculate acceleration and tension produced in string when string is attached at it's ends with two bodies of masses such that $m1>m2$ and the tension ...
10
votes
2answers
571 views

Why does electric force depend on the medium?

Comparing the equations for the gravitational and electric force $$\vec{F}_g=-\frac{Gm_1m_2}{r^2}$$ and $$\vec{F}_e=\frac{Kq_1q_2}{r^2}$$ I noticed the only major difference between them is that ...
0
votes
0answers
44 views

Why is there not always a force in the direction of motion?

This was a question on a physics competition. A girl throws a teddy bear straight up. Consider the motion of the bear only after it has left the girl’s hand but before it touches the ground, and ...
0
votes
1answer
197 views

Inclined plane, circular motion and the friction

Suppose we have a cylinder on an inclined plane of mass $m$ and radius $R$ moving without sliding (so that $\varepsilon = a/R$). Why is the friction $F$ causing the circular motion sometimes lower ...
0
votes
2answers
249 views

Work and free body diagrams

I am a bit confused with how to find work when there is a free body diagram. I am trying to work out this problem, and in it a box is being pulled at a constant speed by a rope at a constant angle ...
0
votes
3answers
199 views

Centripetal and centrifugal force

If a stone is rotated with the help of a rope, then both centripetal force and centrifugal force will be liberated. The magnitude of that forces are same, but direction of them are opposite to each ...
1
vote
3answers
172 views

Where Potential increase gets it's energy from?

Imagine there are two particles: A,B; of which, we observe A to be stationary, while B is moving towards A at velocity v. A,B has same mass; and they are charged both positive. B has a potential wrt ...
5
votes
1answer
245 views

Force problem related to adhesive and bonding

I have two PCBs (printed circuit board), and they are glued by adhesives, as show in the pictures. And the location of the adhesives are indicated on the picture (please notice that NO adhesive is ...
1
vote
1answer
298 views

Force of a solenoid on a ferromagnetic material

As I was trying to find an answer to another problem, I was informed that the equation I was using would not work. The equation I was using was $$F = (NI)^2\mu_0\frac{\text{Area}}{2g^2}$$ If this ...
0
votes
1answer
41 views

Path of a swinging object on a rope [on hold]

With my lanyard in hand (weighted by my keys), a gentle swinging motion will put the keys in pendulum motion, swinging back and forth. Pendulum motion is relatively easy to model since it is ...
1
vote
1answer
94 views

How does force transmit through a solid block?

If you take a solid block, say, a cube of side length $l$ with density $\rho$, you place it upon a solid floor, and you apply an external pressure of $p(x,y)$ on the upper face ($x$ and $y$ define a ...
0
votes
1answer
137 views

Calculating output forces of bicycle wheels

Based on the force on the rear gear $F_t$ and the radii of the rear gear $R_g$ and rear wheel $R_w$ , how would you calculate the force the bicycle exerts on the ground when it is accelerating? I ...
0
votes
3answers
2k views

Drag force on a flat plate

The solution for this apparently is $\frac{1}{2}C \rho A V^{2}$ where $C$ is the drag coefficient, $A$ is the area and $\rho$ and $V$ are the wind density and velocity. Let's do it without the drag ...
-2
votes
0answers
28 views

Downforce formula [on hold]

I need a formula force calcuating the down force generated by a NASCAR. I have done research and found some answers on google but i don't know what the formulas mean. So i was wondering if any body ...
2
votes
3answers
59 views

If I push my hands against each other, why does the stronger one move the weaker one if the forces should be equal and opposite [duplicate]

If I were pushing my hands against each other, the stronger arm will move the weaker arm, but if all forces have an equal and opposite reaction, why does the weaker one move?
4
votes
3answers
109 views

Which force to resolve?

In the above image the particle is effectively moving 'out of the page' in circular motion. We want to solve for $\alpha$, the slope is smooth, and the particle is moving neither up nor down the ...
2
votes
1answer
51 views

Would the Moon be able to take water from Earth?

I know that if you add mass to the moon, it would get closer to the Earth. We all know that the moon causes the tides because it's gravity pulls the water. So, my question is: If the moon gained more ...
5
votes
3answers
4k views

The force arrow for centripetal force points in the opposite direction of my calculation?

I need someone to clarify a conceptual problem I can't seem to surpass. Image there is a rollercoaster loop and a rollerbcoaster car enters the loop at high speed. Once the car completes the full ...
0
votes
3answers
48 views

Conditions for the tension to vary in the rope

What are the conditions for the tension to vary in the rope. I have read below conditions 1. rope has to have some mass 2. rope is accelerating I get the 1st ...
1
vote
2answers
165 views

If the force of friction is 20 N for a moving body does acceleration increase with the increase of the mass?

A body is moving and the only force acting on it is the force of friction. If we put another body on this moving body somehow the force of friction will increase; does its acceleration change?
1
vote
1answer
48 views

What makes cart with a moving object in it gain speed (no friction anywhere)?

I would like to understand what makes the cart below the moving object move. There is no friction between any of the objects. The cart is moving therefore there is force applied to it. The only force ...
0
votes
2answers
107 views

Force on border exerted by a liquid

Why is it nearly universally understood that force in a liquid against a border is dependent on internal pressure, depth only, rather than weight of the liquid? Thus, for example, that the force from ...
0
votes
1answer
14 views

Resultant force and constant velocity

Let's say for example, Jack is pushing on a box with force $F$, and John is pushing from the opposite side with force $F$ as well. We say that there is no resultant force, and the box remains stable ...
0
votes
1answer
24 views

Massless rope in a pulley pulled by a person

A massless rope passes through a pulley. On each end of the pulley there is a different mass (object). A person grips one of the masses and thus the system comes to equilibrium. How would you ...
1
vote
1answer
29 views

Does the shape of a containter affect the apparent mass of liquid inside it when measured by a scale? [duplicate]

For both containers it is true that: $p_{bottom}=p_{atm}+\rho gh$ and $F_{bottom}=a*p_{bottom} \iff F_{bottom}=a*p_{atm} + a\rho gh$ I do not know how a scale functions, but I guess that the only ...
0
votes
2answers
36 views

Objects and forces: air resistance

A force always works between two objects. When we are talking about air resistance acting on a skydiver for example, would air be considered the second objects besides the skydiver?
2
votes
4answers
328 views

Will this rope break due to the tidal forces or not?

While I was thinking about how tidal forces can make objects float at the surface of a planet orbiting a massive object like a black hole, the fact that any material on the Earth isn't held together ...
0
votes
1answer
34 views

Doubts About Force and Inertia!

But then what does inertia mean at all!? Cant we calculate how much it resists the applied force? I mean considering an imaginary plane with no friction but gravity as of Earth and an enormous mass of ...
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votes
0answers
26 views

Force required to swing gate open/close

I need to know how to calculate the force required to swing the gate open / close. If it is moving straight, we can use f=ma, but how to calculate for swinging motion? When I open or close the gate, I ...
1
vote
3answers
136 views

When does normal force equal to $mg$?

Can someone once and for all explain when does normal force equal to mg? I know for sure that when there is no friction, normal force will be equal to mg. But, i encountered some questions when there ...
0
votes
1answer
47 views

Two mass spring system

The equations of motion of the spring mass system with, m = 1 $ \ddot{y_1} = -k_1y_1 + k_1(y_2-y_1)$ $ \ddot{y_2} = -k(y_2-y_1) - ky_2$ My question is with the second term in the first equation. ...
1
vote
1answer
35 views

Might one fall out of a basket swing?

My nieces like being pushed high in a basket swing. My sister-in-law worries they will fall out. Assuming I don't push them above horizontal, that I don't catch the basket and stop it mid-swing, and ...
0
votes
2answers
30 views

Magnitude of Tension: Circular Motion [closed]

Please consider the following: A tennis ball connected to a string is spun around in a vertical, circular path at a uniform speed. The ball has a mass m = 0.165 kg and moves at v = 4.76 m/s. The ...
0
votes
0answers
36 views

Constant Velocity and Forces [closed]

I understand that if an object is maintaining constant velocity, then the net force is zero. With that said, the force due to friction equals the applied force, right? What if you were to diagram ...
0
votes
3answers
49 views

Tension in rods (basics)

I have a problem understanding these basics. What is the tension in the ground rod due to the forces exerted by the slanted rods? Please feel free to correct me at any point. Rods are idealized ...
0
votes
3answers
451 views

Advantages/Disadvantages of “hanging off” a motorcycle when leaning

The closest question I could find with regards to this subject was this one: Countersteering a motorcycle However, it does not address the specific physics of what I would like to know. There are 3 ...
-2
votes
1answer
71 views

Boeing 737 Homework Problem [closed]

I have done the above problem, but have come out with a rather large surface area. Could someone point out my mistake(s)? Given/Assumptions: I assume $\sum F_y=0$ because it's level and straight. ...
0
votes
3answers
31 views

Effect of internal force on the weight of an object

A man is holding a closed cage on the palm of his hand with a bird in it. When the bird flies with an upward acceleration inside the cage, it feels heavier. But the force due to the bird in the cage ...
1
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0answers
23 views

What forces act on a caravan being towed by a car? [closed]

What forces act on a caravan that is being towed by a car? How does this compare to a simple car travelling at a constant speed?
1
vote
3answers
4k views

Forces on a ball thrown upwards

When a ball is thrown up in upward direction, it is said that force is in downward direction. Why we don't we consider the force given to the ball to throw up in the upward direction? Is there is no ...
1
vote
0answers
20 views

Calculus formulas for buoyant force?

I am launching a high-altitude balloon as a part of a physics project I am working on. I know that the amount of helium I need corresponds to about 40 newtons of lift for the launch, which is all I ...
0
votes
1answer
121 views

Explanation about friction force directions of two moving bodies in contact

can someone explain me why in this scenario (picture below) we have a friction force Ftr12 in the same direction as movement (left part of the picture, case 1 ) and how these directions of friction ...