Surface tension is the tendency of liquid surfaces at rest to shrink into the minimum surface area possible. Surface tension is what allows heavier than water i.e., denser than water objects such as razor blades, insects (e.g. water striders), to float and slide on a water surface without becoming even partly submerged.
At liquid–air interfaces, surface tension results from the greater attraction of liquid molecules to each other (due to cohesion) than to the molecules in the air (due to adhesion).There are two primary mechanisms in play. One is an inward force on the surface molecules causing the liquid to contract. Second is a tangential force parallel to the surface of the liquid. This tangential force (per unit length) is generally referred to as the surface tension. The net effect is the liquid behaves as if its surface were covered with a stretched elastic membrane. But this analogy must not be taken too far as the tension in an elastic membrane is dependent on the amount of deformation of the membrane while surface tension is an inherent property of the liquid–air or liquid–vapour interface.Because of the relatively high attraction of water molecules to each other through a web of hydrogen bonds, water has a higher surface tension (72.8 millinewtons (mN) per meter at 20 °C) than most other liquids. Surface tension is an important factor in the phenomenon of capillarity.
Surface tension has the dimension of force per unit length, or of energy per unit area. The two are equivalent, but when referring to energy per unit of area, it is common to use the term surface energy, which is a more general term in the sense that it applies also to solids.
In materials science, surface tension is used for either surface stress or surface energy.
Hi Guys...
I have a small doubt regarding surface tension.
When calculating the relation between Pressure Difference inside and outside a Droplet and Surface Tension, we multiply Pressure Difference with Cross Sectional Area of the Droplet and equate it to the Surface tension force.
My doubt is...
For the case of a particle attached to an inextensible string which is hanging at rest and then provided an impulse horizontally, what conditions must the system meet in order to allow for COMPLETE circular motion. I am well aware the tension at the apex of the motion must be satisfy one of the...
Homework Statement
In order to raise a mass 'm' a man ties it to a rope and passes the rope over a friction less pulley. He climbs the rope with an acceleration 3g/2 relative to the rope. If the mass of the man is m/2 and the mass of the rope is negligible, the tension in the rope is
a) 3mg/2...
Homework Statement
Two identical conducting balls, b1 and b2, each with a mass of 25.0g
both are hanging at 50.0cm at an angle of 45Degrees from the vertical each.
Homework Equations
Fg = mg
Fe = kq/r^2
Ft = ?
The Attempt at a Solution
I made a free body diagram and am confused on what to do...
I'm having trouble solving this problem. I did Google the solution with the steps, which I managed to actually get right in all aspects except for a small part in the trigonometry that throws me off.
I drew my FBD's correctly, hopefully. I'm not sure how I can draw nice looking FBDs online...
Homework Statement
A pendulum consists of a bob of mass A hanging from a string of non-zero mass m. Its maximum displacement is p/4 [whatever that p means, I do not know. the question writers do a poor job of writing questions]. What is true of the tension in the string?
1) It is greatest...
There's two questions about tension(the force), that no matter how much I try to find answers to and understand since the past few days, I'm simply not able to. Any help in this matter would be highly appreciated.
1) If person A and person B are holding a rope, and person A applies 100N of...
Homework Statement
Hi, sorry, I am not good at writing English, but I am trying. I hope that someone helps me solve the following problem.
http://hodol.kr/q.jpg
Please refer to the figure above.
A stick(AB) of length 5 is leaning against the Wall(AO) and a string(CO) is tied at the...
Homework Statement
A person would like to pull a car out of a ditch. This person ties one end of a chain to the car's bumper and wraps the other end around a tree so that the chain is taut. The person then pulls on the chain perpendicular to its length. If the distance between the car and tree...
I am tasked to find the tensions of two wires by calculating the "magnitude of the vector" in a high school physics/precalc class. I have tried working out the equation in several ways but they all end up in an unsolvable format. So, in reference to the picture, A = 35 degrees, B= 30 degrees and...
Having trouble to understand a classical example of surface tension:
Two balloons are connected to each other with a valve. If the surface tension of the two balloons is the same but one balloon is bigger than the other, when the valve is lifted open so the air in the two balloons is now...
Q: In a tug of war between 2 athletes, each pulls on the rope with a force of 200N.
a) What is the tension in the rope?
b) If the rope does not move, what force is each athlete exerting on the ground?
I wrote for both a) and b) 200N, and I am unable to confirm this because my textbook has no...
I have a physics homework question that i need help with;
A submerged ball of negligible mass is attached to the bottom of a swimming pool by two strings as shown. The volume of the ball is 5000cm^3. Calculate the tension in each string. (hint you need to look up the density of water)
How do i...
a thin uniform rod of length l and density d is rotating with angular velocityω about an axis passing through one of its ends and perpendicular to it.find the tension int the rod as a function of x.(x= dist from axis of rotation).area of cross section = a
attempt at solution...
Homework Statement
A bungee jumper of mass 60kg jumps from a bridge 24 m above the surface of the water. The rope is 12 m long and is assumed to obey Hooke's law. What should the spring constant of the rope be if the woman is to just reach the water?
Homework Equations
Ep=mgh
E=1/2 kx^2
The...
Homework Statement
The figure below shows a light truss formed from three struts lying in a plane and joined by three smooth hinge pins at their ends. The truss supports a downward force of = 1 330 N applied at the point B. The truss has negligible weight. The piers at A and C are smooth.
The...
"A 2.4% Determination of the Local Value of the Hubble Constant" by Riess et al has led to some excited news stories recently. I don't see it discussed anywhere here. Looking for the essence of the paper, I note three things:
The two measurements considered are "the Hubble constant ... measured...
Homework Statement
A 0.02 m x 0.01 x 0.03 block of copper (density = 8.8 g/cm3) is suspended submerged in milk (density = 1.03 g.cm3) by a string. How much tension is in the string?
Homework EquationsThe Attempt at a Solution
My initial thought for an equation was:
T+Fb(buoyancy)-mg=0
T+...
Homework Statement
Is it possible to solve for the magnitude of tension without using the mass of the object? : You use a string to suspend a cork ball with a mass of 22g from the ceiling of a moving speedboat. The ball and the string hang at an angle of 32.5degrees from the vertical. The...
Let's assume that the force of friction is only present between the two blocks and that the pulley is massless. On top of that, force F pulling the two blocks at a constant velocity; as a result, the acceleration = 0m/s2.
May someone tell me how many forces of friction are going on between the...
I have a doubt regarding the definition of rotational work, which is as follows
W = \int \tau_z d \theta
Where \tau_z is the component of the torque parallel to the axis of rotation z.
My doubt concerns the fact that, looking at this definition, it seems that any torque which has an axial...
Homework Statement
A 50.0 kg 6.00m awning is held up by a wire in the middle. A 15kg sign hangs at the end. Calculate the tension in the massless wire and the magnitude of the net force from the wall acting on the awning.
The cable forms a 40 degree angle with the awning at the bottom right...
Homework Statement
A ball of mass m is attached to a string of length L and released from rest at point A. Show that the tension in the string when the ball reaches point B is 3mg, independent of the length l. (there is an image in attachment )
[/B]
Homework Equations
K = mv2/2
U = mgh
Fcp =...
Homework Statement
A block with mass m1=15.0kg is on a rough inclined plane and is connected to an object with mass m2=25.0kg as shown. The rope may be considered massless; and the pulley may be considered frictionless. The coefficient of kinetic friction is µk=0.28
Homework Equations
a...
Just signed up, hi everyone!
1. Homework Statement
A man weighs 150 lb, and attaches a bungee cord having a stiffness of k = 500 lb/ft, to his feet.
If he jumps from rest off the side of a bridge, determine the required unstretched length of the
cord so that he can just touch the surface of...
If I had a object with a rope tied to it, and I began to pull the object on a surface of zero friction with a force of 4 N, both the object and the rope would start to move at the same acceleration. But I deduced that by intuition, not physics. When regarding all the forces acting on both the...
Homework Statement
A 14.0 kg sign hangs from 2 lengths of rope, each of which is 70.0 cm and at a 20.0 degree angle from the ceiling.
1) What is the tension of the rope?
2) How could you reduce the tension on the ropes for the same sign without adding another rope?
Homework EquationsThe...
Imagine a spring that has its two ends attached to a wall at the same height. The spring will adopt a kind of a ''U'' shape (maybe a parabollic shape would be more precise). Why are the coils near the wall more distant from each others than the coils at the middle of the spring ? I think it is...
Homework Statement
So there is a pulley with 1 mass hanging from it. The string is wrapped around and one end is taped to the pulley so that only one end of the string hangs from the pulley. There is a mass of 100 grams attached to that string. Create a system of equations to find linear...
Homework Statement
calculate the tension in the cable
Homework EquationsThe Attempt at a Solution
the resultant force act on the each metal bar is equal to the tension of each bar . so FR= tension in bar
but , i have problem of finding the the area in FR , i have only (0.75/2)...
Homework Statement
How do you determine the direction of tension in a force/ the direction of tension acting on an object. I'm confused.
Homework Equations
-
The Attempt at a Solution
I have no clue. Help!
Homework Statement
Picture a seat that is supported by two cables. One is horizontal, and the other makes an angle of 40 degrees to the vertical. The swing swings in a horizontal circle at a rate of 32 rev/min. The horizontal cable is 7.5 m long. The person sitting on the seat at the end of the...
Homework Statement
You are lowering two boxes, one on top of the other, down the ramp shown in the figure (Figure 1) by pulling on a rope parallel to the surface of the ramp. Both boxes move together at a constant speed of 19.0 cm/s . The coefficient of kinetic friction between the ramp and the...
Homework Statement
The ramp in figure is frictionless. If the blocks are released from rest, which way does the 10 kg block side and what is the magnitude of its acceleration? θ=40°...
Homework Statement
The County Fair Swing carries the mass of riders and chairs in a circular path in a horizontal plane while suspended by cables or chains. Let's assume that:
Each chair with riders is supported by a single cable
The tension in the cable equals 2 x the total weight riders...
Homework Statement
A rope is hanging vertically straight down. The top end is being vibrated back and forth, and a standing wave with many loops develops on the rope, analogous (but not identical) to a standing wave on a horizontal rope. The rope has mass. The separation between successive...
Homework Statement
Homework Equations
I am Stuck getting Theta out of the last step of equation. I have found that theta is 35 by trial and error.( i wrote an excel program)[/B]The Attempt at a Solution
Homework Statement
A 10.0 kg sphere is attached to the incline by a horizontal string. Whats the tension in the string.
Homework Equations
sum of all horizontal forces = 0
sum of all vertical forces = 0
sum of all torques = 0
The Attempt at a Solution
The sum of the horizontal forces[/B] is...
Homework Statement
A ball with a mass of 3.0 x 10-4 kg hangs from a 15 cm long thread between two parallel plates. The thread is deflected to the side, as shown in the following diagram. The charge on the ball is +5.0 x 10-5 C.
a) Find the tension in the thread
b) Find the magnitude and...
Homework Statement
"An elevator cab and its load have a combined mass of 1600 kg. Find the tension in the supporting cable when the cab, originally moving downward at 12 m/s, is brought to rest with constant acceleration in a distance of 42 m."
##m = 1600 kg##
##v = 12 m/s##
##d = 42 m##...
I conducted a uniaxial tension test for a variety of materials but wasn't able to gather much useful axial strain data due to the extensometer continually slipping. I have axial strain data for the linear elastic region of the stress strain curve and I also have the extension of the crossbar of...
Homework Statement
A student tries to raise a chain consisting of three identical links. Each link has a mass of 200 g . The three-piece chain is connected to a string and then suspended vertically, with the student holding the upper end of the string and pulling upward. Because of the...
Homework Statement
A helicopter is flying at a constant altitude towing an airborn laser at 129kg. Both the chopper and the sensor move only horizontaly and have a acceleration of magnitude 2,84 m/s2. ignoring air restitance find the tension on the cable towing the sensor.
Homework Equations...
Homework Statement
-------------------------------------
|.\
|...\
|...\
|...\
Q...O P
O=the bob
Teta=60 degree
The bob of a simple pendulum is released from rest at P. The mass of the bob is m and...
a thin film of water has surface tension due to the strong bonds present on the surface in order to counteract the net downward force and this increases the potential energy of the surface layer of particles therefore on a
hydrophobic surface it forms a water droplet , my question is since it...
These buckets are being suspended. The cords have no mass and each bucket is 3.5 kg.
a.) Find the tension in the upper cord (T1) and the lower cord (T2)
b.) If the apparatus is pulled upwards from the top of the upper cord, what are the new tensions of each cord?
I understand the...
Homework Statement
Two trucks tow a third one by means of inextensible ropes and a pulley attached to them (fig. 1). The accelerations of the two trucks are a1 and a2. What is the acceleration of the third truck that is being towed?
(fig.1) is in this link (I'm sorry, I don't know how to post...
[mentor's note: Spilt from https://www.physicsforums.com/threads/tension-questions.852525]
How does friction in a pulley or a rotating pulley change the uniform tension in a rope that was present in an ideal situation? Thanks!