Tension Formula: Explanation and Solved Examples

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The Tension Formula is commonly used to calculate the tension force exerted on any object.

  • Push, pull, thrust, lift, weight, friction, and tension are all names for forces.
  • Tension is the pulling force that is transmitted along the length of a flexible object, such as a string, cable, or chain.
  • It can also be described as the force that is exerted on each end of a rigid object, such as a rod or beam.
  • In both cases, tension is an action-reaction pair of forces, meaning that the force exerted on one end of the object is equal and opposite to the force exerted on the other end.

Key Terms: Tension, Force, Gravitational force, Action-reaction force, Tension force formula, Weight, Push or pull


Tension

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The pulling force transmitted axially by a string, rope, chain, or similar objects, or by each end of a rod, truss member, or similar three-dimensional object, is referred to as tension.

  • In Latin, the word "tension" means "stretching".
  • All physical things that come into contact with one another can exert forces on one another.
  • Depending on the types of objects in touch, we call these contact forces by different names.
  • The force tension is what we call it when one of the things applying the force is a rope, string, chain, or cable.
  • It is essential to know that tension is a pulling force because ropes cannot effectively push.
  • When you try to pull anything with a rope, it becomes slack and loses the tension that allowed it to pull in the first place.
  • This may seem self-evident, but when drawing the forces acting on an object, students frequently draw the force of tension in the wrong direction.
  • Remember that tension can only pull on an object.

Tension Formula

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Tension is a force acting along the length of a medium, particularly one that is flexible, such as a rope or cable.

The formula of tension is given by

\(T=mg\pm ma\)

Where

  • T is the tension force
  • m is the mass of the body
  • g is the acceleration due to gravity
  • a is the acceleration of the moving body
  • mg = W is the weight of the body

Cases:

  • When the body is moving upward, then the tension will be T = mg + ma
  • When the body is moving downward, then the tension will be T = mg – ma
  • When the tension is equivalent to the weight of the body T = mg.
Tension Formula
Tension Formula

Also Read: 

Surface Tension Pressure of Ideal Gas

Solved Examples

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Ques. A light and inextensible string supports a body of mass of 25 kg hanging from its lower end. If the upper end of the string is firmly attached to a hook on the roof, then what is the tension in the string?

Ans. Since the mass attached to the string is not moving, therefore the tension on the string is given by

T = mg

Given the mass of the body, m = 25 kg

⇒ T = 25 x 9.8 = 245 N

Ques. A body of mass 10 kg is dangling at the end of a string. If the acceleration of the body is

  1. 5 m/s2 in the upward direction
  2. 5 m/s2 in a downward direction

Find the tension in the string.

Ans. Given, the mass of the body, m = 10 kg

  1. If the body moves in the upward direction, then tension in the string is given by

T = mg + ma

⇒ T = (10 x 9.8) + (10 x 5) = 148 N

  1. If the body moves in the downward direction, then tension in the string is given by

T = mg - ma

⇒ T = (10 x 9.8) - (10 x 5) = 48 N

Also Read: 

Surface Tension Buoyant Force Effects of Forces: Types (Contact& Non Contact), Effects
Non Contact Force Pseudo Force Central Force

Things to Remember

  • Tension is a force acting along the length of a medium, particularly one that is flexible, such as a rope or cable.
  • Tension force is always a pulling force.
  • The net force acting on an object can be calculated as Fnet = T − W = 0
  • The formula of tension force is given by T = W ± ma = mg ± ma
  • If the body is moving upward, the tension will be T = W + ma. 
  • When the body is moving downward, the tension equals T = W – ma. 
  • T = W if the tension is equal to the weight of the body.

Sample Questions

Ques. What is the force of tension? (1 Mark)

Ans. Tension force is the pulling force exerted axially along the length of a rope or cable.

Ques. A 15-kilogram body is suspended from the bottom end of the light and an inextensible cord. What is the tension in the string if the top end of the rope is firmly secured to a hook on the roof? (2 Marks)

Ans. Because the body is hung and not moving, the tension in the string will be equal to the body's weight. 15 kg = m

T = W = mg = 15 × 9.8 = 147 N 

Ques. Is tension a non-contact or contact force? (1 Mark)

Ans. When a surface comes into direct contact with a rope, tension is created. As a result, it's a contact force. 

Ques. A mass of 8 kilograms is dangling from the end of a thread. If the mass accelerates in the
(a) upper direction at a rate of 3 m/s2.
(b) 3 m/s2 in the direction of descent.
Then determine the tension of the thread. (3 Marks)

Ans. The following parameters are provided:

m = 8 kg, g = 9.8 m/s. 

(a) Assuming a = 3m/s2.

The tension force is T = mg + ma = 8×9.8+8×1.5 = 90.4 N if the body is moving upward.

(b) Assume a = 3m/s2.

The tension force is T = mg – ma = 8×9.8–8×1.5 = 66.4 N, if the body is moving downward.

Ques. A monkey weighing ten kilograms climbs at a speed of two metres per second up a light vertical string strung from a hook. Determine the string's tension (take g = 10 m/s2).  (3 Marks)

Ans. Given, m =10 kg, g = 10 m/s2, and a = 2 m/s2

The tension in the rope will be equal to the apparent weight of the monkey as the monkey accelerates up.

i.e., T = m (g + a) = 10 (10 + 2) = 120 N 

Ques. A ten-kilogram mass is dangling on a thread. If the mass's acceleration is as follows:
(a) A speed of 5 metres per second in the uphill direction.
(b) A downward velocity of 5 metres per second.
Calculate the thread's tension. (3 Marks)

Ans. We've been given the following information:

m = 10 kg, g = 9.8 m/s2, a = 5 m/s2 

(a) The tension force is T=mg+ma when the body accelerates upwards.

T =10(9.8+5)

T =148N

(b) The tension force is T = mg – ma while the body is moving downwards.

T=10(9.8–5)

T = 48 N

Ques. What are the applications of tension force? (3 Marks)

Ans. The following are the applications of tension force

  • It is used to pick up lightweight things in a crane machine.
  • It is used to pull automobiles or cars on a busy highway or road.
  • Weighing balances employ tension forces.
  • They are also utilized for a variety of gym equipment.

Ques. What are the different fundamental forces? (3 Marks)

Ans. The following are the fundamental forces

  • Gravitational force
  • Electromagnetic force
  • Strong nuclear force
  • Weak nuclear force

Ques. What is the unit of tension? (1 Mark)

Ans. The unit of tension is Newton (N).

Ques. List five non-fundamental forces. (2 Marks)

Ans. The following are the non-fundamental forces

  • Friction
  • Tension
  • Normal reaction
  • Centrifugal force
  • Centripetal force

Also Read:

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