What is Tension: Definition and 1000 Discussions

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.

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  1. K

    I Horizontal Tension Force equation

    (not a homework question - I left education over 45 years ago) Hi, this just out of interest as I have been googleing this and can't find the answer I know the equation for tension force, for example a weight on a string, block on a ramp, etc. But is there something similar for a horizontal...
  2. jamiebean

    Understanding Tension Force: A Beginner's Guide to Physics

    I am new to physics I have no idea how the forces work and how to calculate the tension with f=ma thank you very much..
  3. Frigus

    What causes tension in a rope moving in a vertical circle?

    I don't get how ball moves in a vertical circle,we say tension provides centripetal force to the ball, i have posted a image in this post and in I which I have shown that their is a downward force mg and upward velocity,in this what will cause tension in the rope...from non inertial frame it is...
  4. V

    Tension forces of two wires in comparison to the gravitational force

    The correct answer is the second one. I honestly have no idea why this is so. I understand that the right rope has less tension that the left one since it's at a shallower angle from real world experience, but I don't really know why this is so, let alone how the forces compare to gravitational...
  5. E

    My understanding of tension is a little loose....

    A video on the MIT open courseware site, https://ocw.mit.edu/courses/physics/8-01sc-classical-mechanics-fall-2016/week-2-Newtons-laws/7.1-pushing-pulling-and-tension/, defines tension as the magnitude of the force between any two adjacent segments (A and B) of string - that is, ##T =...
  6. E

    How can I calculate the tension force?

    This is my attemp of solution: Since the formula to calculate the tension is T=mg I first calcualted the weight of the bridge with the ecuation W= mg m=W/g m= 18,000 N / 9.81 m/s m= 1834 kg So T=(1834)(9.81)= 17,991 N But this seems no logical to me because the Tension force is a bit less...
  7. R

    Find the accelerations of all three blocks and the tension in the rope

    I am thinking about solving it this way. The first three equation is from Newton law. Then the forth one is the constrain equation, after that I simplified the first three equations, and I am thinking about plugging them into the forth equation and solve for T after that I get the value of...
  8. R

    Tension in a rope wrapped around a shaft, pulling in a mass

    Hi everyone, I am thinking of solving it this way. Since Fc=mw^2r. and Fc=T. Then -dT=dmw^2r. where dm=m1(dx/l). and putting the lower at x=l the tension will be T=m2w^2l. Am I doing things right.
  9. I

    Understanding Tension in Angles: Expert Insights and Tips

  10. Vivek98phyboy

    Force due to Surface tension here

    Why does the force due to surface tension act parallel to the surface here? I know that surface tension is a result of absence of cohesive force above the surface and thus the water molecules below pulls the surface down and keeps it like a stretched membrane. If the surface is pressed as...
  11. C

    Climbing with Tension: Exploring Muscle vs. Mechanical Energy

    Here the upward force on the camp is Tsinx <=360 Therefore T(max)=720N Here they have taken the equation that T-mg=ma This shows that the man is climbing due to tension. But I can't visualise how tension helps in climbing. Isn't it our own energy that helps us to climb. The muscle energy gets...
  12. Vivek98phyboy

    Reason for Calculating Surface tension

    When calculating force due to surface tension across a hemispherical drop, we look at only the circumference and multiply it by the value of surface tension. When we know that it is the surface tension which is responsible for the curved surface of the liquid drop, why don't we calculate the...
  13. C

    What is the tension force at the top of a spring?

    Good afternoon, I have some doubts about the tension force suffered by a spring to which a mass is hung and which is making a simple vertical armoin movement. My doubt lies in the fact that at the bottom of the pier (where the mass hangs), the spring exerts the restoring force that is given by...
  14. E

    Circular Motion/Energy: Find the position of the rings when tension = 0

    Here's my first attempt at a solution: First, I calculated the speed of one ring at the point where the tension would be zero. 3mgr(1-cosΘ ) = (1/2) * (3m) * (v^2). 3m * v^2 = 6mgr(1-cosΘ) Next, since I wanted the centripetal force, I took the result I got and divided by the radius. Fc =...
  15. harsh22902

    Surface Tension and Capillary Rise

    According to this definition I am unable to understand why does surface tension acts tangentially to surface of contact of liquid and capillary tube. And is the force of surface tension balancing the adhesive forces which lead to capillary rise OR it is the reason behind the capillary rise?
  16. N

    Is my solution for the Bungee Tension Problem correct?

    Hello again, I did a sum of the forces at the top and bottom of the motion and got: Top...mg=ma Bottom...T-mg=ma Got T=2mg when I substitute the mg in for ma at bottom.Then I assumed kx=T=2mg so x(length of cord) would equal 2mg/k Then V of wave would be ...sq.rt2mg/k Is it that simple? Feel...
  17. A

    How Do You Calculate the Tension of a Cello String?

    wavelength of string= 2*L wavelength of string=2*0.70m= 1.4m velocity of string= frequency * wavelength velocity of string= 220Hz * 1.4m= 308 m/s tension= (308m/s)^2 * 0.00196 kg/m =186N Is the tension correct?
  18. Kaushik

    Factors affecting surface tension

    I read the following two points: Temperature is indirectly proportional to surface tension. Adding impurities affect the surface tension of the molecules. Adding soluble impurities increases the surface tension whereas adding sparingly soluble impurity decreases the surface tension. Why...
  19. F

    Correct understanding of the tension force

    Hello, I am reviewing the concept of tension, a force that expresses the internal tensional state in a body (rope, chain, string, solid body). My understanding is that the force of tension "derives" from the stress tensor and relates (it is the product) the diagonal tensor components to an...
  20. Arman777

    I Is There really a Hubble Tension?

    There has been a lot of Hubble Tension questions and I know its kind of boring ( maybe for some people) but this seems interesting. I find this article https://arxiv.org/pdf/1911.06456.pdf It claims that "The results are shown in Figure 1 which makes it evident that the derived value of...
  21. M

    Exploring the Relationship Between String Tension & Audio Output Amplitude

    I am working on a guitar/piano synthesizer for my own interest. When a string is plucked or struck, tension increases causing a slight pitch bend and change in the inharmonicity. This change then settles as the note quiets down. Thus it is important to model how the tension rises above baseline...
  22. Kaushik

    Tension of a rod rotating on a horizontal table about a vertical axis

    If a rod is on a table (horizontally) and rotating about an axis that passes through one of its ends and vertical to the table, what would be the tension on the opposite end of the rod (the end opposite to the axis) . In this post (Check this post out from Socratic QnA), the limits take while...
  23. P

    Why is tension (T) only added to one side of an Atwood Machine?

    I solved for a1 prior to the force (f) being added. -a1 = a2 and T = m1*a1 + m1*g T = m2*a2 + m2*g <--substitute -a1 = a2, multiply everything by -1, add the two equations in order to solve for a1 (and thus also a2) T = m1*a1 + m1*g -T = m2*a1 - m2*g 0 = m1*a1 + m1*g + m2*a1 - m2*g...
  24. telephonedude

    How do I calculate the tension on top of a pole?

    Let's say I have a 1 meter steel pole with a diameter of 10 centimeters standing upright, and I have a cement block of 30 cm length and 10 cm width and an assumed weight of 5 kilograms. If I place the cement block on top of the steel pole, assuming that neither the pole or the cement block tips...
  25. P

    Whats the tension T' in string 1 if tension of highlighted string is T

  26. P

    Can a tension constraint lead to the wrong results?

  27. A

    Understanding Sign Conventions in Elevator Tension Problems

    So the first thing that I did was solve for the acceleration of the elevator, given the velocities and distances given in the question. My question regarding this issue is not so much the procedure needed to solve the question, but rather the sign conventions for the values given and calculated...
  28. brotherbobby

    What is the maximum tension and friction force for a block held on an incline?

    (a) Ridiculously simple though it looks, I can't see how the string will be tight. One of the two has to be true. (1) The static friction ##f_S = mg \sin\theta = 25\times 10\times \sin 30^{\circ} = 122.5\; \text{N} ##. The maximum static friction ##f_S = \mu mg \cos \theta = 0.6\times 25\times...
  29. kepherax

    Tension in Rope using Torque? Did I do this correctly?

    I think I understand but just want to check if I did this correctly, or if there is more to it...
  30. Frigus

    Surface Tension: Why Tangential and Not Downward?

    Why direction of surface tension is tangential to the surface and not perpendicular downwards since it is caused by molecules in the bulk?
  31. brotherbobby

    Tension in a rotating rod at various places

    (The answer given in the text says ##\boxed{T_1\; >\; T_2}## but, as I show below, I think it's just the opposite). I begin by putting an image relevant to the problem above. Taking a small particle each of the same mass ##m## at the two positions, the centripetal forces are ##T_1 =...
  32. Frigus

    Classical Resnick Halliday Walker -- do they discuss surface tension topic?

    Is surface tension topic present is resnick halliday walker, principles of physics 10th edition,if present then please tell me on which page
  33. lemon__meringue

    What is time average of tension?

    Summary: My homework question asks: Consider a simple pendulum, undergoing small oscillations. Is the time average of the tension in the string of the pendulum larger or smaller than mg? By how much? My homework question asks: Consider a simple pendulum, undergoing small oscillations. Is the...
  34. P

    "Tension: T1 vs T2 - What is Correct?

    Homework Statement: Which part of the statement isn’t correct and which is? Is the tension larger in T1 or T2. Homework Equations: Fnet=mg The sum of the two tensions must equal the mass x gravity or weight since the mass is not moving so the force of gravity must equal the force of tension...
  35. Asterast

    Tension in the string while it descends

    so I took string below point A and Block as a system. Taking mass of string below point A as m and mass of block M. Taking downward direction as X axis. I get Mg+mg-T, Taking T as tension by upward part of string. Now the question says about block descending with acceleration a. so again forces...
  36. Like Tony Stark

    Body connected to two parts of a rope on an inclined plane

    The thing is that my professor said that if the velocity of ##A## is ##400 cm/s##, the velocity of ##B## is ##200 cm/s## because "##B## is connected to two parts of the rope and ##A## is conected just to one part", and he also said that that ##200 cm/s## is the velocity of ##B## with respect to...
  37. Like Tony Stark

    Acceleration and tension of a block on an inclined plane

    I considered the downwards direction and left direction as negative. For ##m_1##, Newton's equations are: ##x) Fr + W_x - T=0## ##y) N - W_y =0## For ##m_2##: ##y) T - W =0## Then, if I replace the data, I get ##T=22.2 N## and then ##m_2=2.2 kg##. With that, for the second question ##m_2=4.4...
  38. S

    Tension and speed of bowling ball pendulum passing the equilibrium position

    For part a I used conservation of energy. -m*g*cos(θ)*L+1/2*m*0^2=-m*g*L +1/2*m*v^2 => v = sqrt(2*g*L(1-cos(θ )). b) For b I was think that T = mg in the equilibrium point but that doesn't invole θ in the answer. So that's why I tought that T*cos(θ ) = mg. So that the tension is mg/cos(θ). But...
  39. S

    Tension in a String: Solve for Unknown Lengths - 98.6N

    I know that the answer has to be 98.6N. So I know that Fy=0 so that 2*T*sin(theta) = 147.25. Then I was think to take the torque of the left wheel but I can't find the lever arm of the tension force. I also know that u can solve the question by saying that the 2 sides of unknown length are 1.5 m...
  40. M

    A Explaining the Hubble tension with fundamental physics

    The Hubble tension or Hubble discrepancy is a contradiction between the Hubble constant as measured today, and the Hubble constant as measured in the early universe and extrapolated to today. @mfb recently listed the relevant measurements. There are some threads about this in the Cosmology...
  41. Kaushik

    B How Does a Man Accelerate While Climbing a Rope?

    A man tries to climb up a rope with acceleration, ## a ##. What does he actually do to climb up? My Interpretation Let the man pull the rope at point A. So the Point A will pull the man with Tension, ## T ##. But at the same time the man is holding the rope, so there will be some normal...
  42. S

    Pendulum's Tension using Force reasoning and Newtons 3rd Law.

    Hi, I have a conceptual question. I was doing some problems on pendulums and found something that confused me. I attached a drawing. I used to always solve these problems by using some trigonometry and trying to find the Tension. i.e. ## m*g = F (of the Tension) * cos(theta) ## so ## \frac...
  43. sumitsumit

    Tension in Rope: Force, Acceleration & Intuition

    i believe there must be some tension while for the force to exert there must be acceleration but my intuition says different
  44. S

    Why does a rubber band's tension grow when stretched?

    My very beginner level understanding is that the rubber band's tension stems from it's particles being held together by it's electric bonds: Atoms and molecules are bound together by their electric charges. And so, When I stretch a rubber band, I am presumably pulling it's particles away from...
  45. K

    Finding the depression and the tension of the string

    I would assume that all the tension in the wire originates from the weight of the mass, and is equal to ##T=mg##, but that is incorrect. Forming a right triangle with a hypothenuse denoted by ##x## and applying Pythagoras theorem: \begin{cases}x^2=y^2+l_o^2 \\ x+y=l_o+\Delta l\end{cases} Solving...
  46. greenrichy

    Solving Newton's Second Law: Tension, Work and Kinetic Energy

    $$\sum F_x = T - w_x - f_k = ma_x $$ $$ T = mg\sin(\theta) + mg\cos(\theta)\mu_k + ma_x$$ $$ T = (9.8 \frac{m}{s^2}) \cdot (\sin(41^{\circ}) + \cos(41^{\circ})) + (75kg)\cdot(0.25\frac{m}{s^2}) $$ $$T = 672.91 N $$ Having found the tension force, I can find the work done by the person who's...
  47. N

    Vertical circle in a pendulum ride -- tension force acting on the gondola

    At the bottom of the circle, the tension force is greater than the weight force as there must be a net force acting towards the centre to provide the centripetal force causing the centripetal acceleration and thus the circular motion. In the equation above (T = mv^2/r + mg) I only have the mass...
  48. M

    Calculate the tension in a rope attached to a ball in circular motion

    The solution to the problem simply states: "Use of mv^2/r = 2000. T = (2000 + 7500) = 9500N". I don't understand this solution. Nothing more is provided. I don't know how you are supposed to find the radius (in order to use the centripetal force formula) merely from the information provided...
  49. solarmidnightrose

    What is knowing the Tension Force good for?

    So, I'm working on calculating the tension force in vertical circles-and I understand how to calculate the tension force at different points in the vertical circle (via vector sums). But what I don't really understand is how to interpret this information. What can I further do with these...
  50. F

    Where is the tension applied in a 3 dimensional cable?

    Hello, I need to transmit motion between a servo motor and a pulley through a cable. In order to do that, I've screwed a pulley to the servo and fix the cable on both the motor pulley and the pulley. I am working in a scale where the radius of the cable cannot be neglected due to a precision...
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