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What is Torque?

What is Torque in Physics?

Torque in physics is a measure of the rotational force applied to an object, causing it to rotate around an axis. It depends on the force applied and the distance from the axis of rotation. In simpler terms, torque is what makes something spin or rotate when a force is applied, and the longer the distance from where you apply the force, the more torque is generated. The SI unit of torque is the newton-meter (Nm).

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Triangle of Forces

Key Points:

A) Torque is considered positive when it produces a clockwise rotation and negative when it results in a counterclockwise rotation.

  1. Clockwise Torque: It causes an object to rotate in the clockwise direction around an axis.
  2. Counterclockwise Torque: It causes an object to rotate in the counterclockwise direction around an axis.

B) Static Torque and Dynamic Torque refer to different conditions in rotational motion:

  1. Static Torque: This is the torque applied to an object at rest, preventing it from moving or initiating rotation. It deals with the resistance to the initial movement of an object.
  2. Dynamic Torque: Dynamic torque comes into play when an object is already in motion and is subjected to a torque that either accelerates or decelerates its rotational speed.

Thus, static torque deals with the initiation or prevention of rotation in stationary objects, while dynamic torque is involved when dealing with the changes in rotational motion of objects already in motion. Both static and dynamic torque help us to understand the behaviour of objects undergoing rotational forces.


Assuming you are trying to open a stubborn jar. Torque in physics is like the twisty force you use to make the lid spin. It’s what helps you open doors, turn a wrench, or even ride a bike.

How Torque Works:
Think of a door. When you push or pull on the handle, you’re applying torque. But it’s not just about the force; it’s also about where you apply it. If you push near the hinges, the door won’t move easily. But if you push at the handle, where it’s far from the hinges, it swings open smoothly. Torque depends on both the force and the distance from where you’re pushing or pulling.

In fancy terms, torque is calculated with this formula: Torque = Force × Distance. If you push harder or pull with a longer wrench, you get more torque.

Everyday Examples:
When you pedal a bike, you are applying torque to turn the wheels. Using a wrench to tighten a bolt? Torque is at work. Even turning the steering wheel in a car involves torque.

Key Idea:
Torque is like the twisty power that makes things rotate. It’s not just about how hard you push or pull, but also about where you apply that force.

How to Calculate Torque

Torque Formula

The torque formula is:

Torque (τ) = Force (F) x Distance (d)


  • τ is the torque in newton-meters (Nm) or foot-pounds (ft-lb).
  • F is the force applied perpendicular to the lever arm in newtons (N) or pounds-force (lbf).
  • d is the distance from the axis of rotation to the point where the force is applied in meters (m) or feet (ft).

Calculating Torque in a Simple System

To better understand the concept, let’s calculate torque in a straightforward scenario. Suppose you have a wrench applying a force of 50 newtons (N) at a distance of 0.3 meters (m) from the axis. To find the torque:

Torque (τ) = 50 N x 0.3 m = 15 Nm

In this case, the torque applied to the system is 15 newton-meters.

Lever Arm Length and Its Impact on Torque

The lever arm length is a crucial factor affecting torque. The longer the lever arm, the greater the torque produced for a given force. Understanding this relationship is vital in various applications, from engineering machinery to using simple tools in daily life.

Angular Velocity and Torque

Angular velocity is another important aspect related to torque. It determines how fast an object rotates around an axis. The relationship between angular velocity and torque is described by the following formula:

Torque (τ) = Moment of Inertia (I) x Angular Acceleration (α)

Units of Torque

In different regions, torque is measured using different units, leading to occasional confusion. In the metric system, torque is measured in Newton-meters (Nm), while the imperial system uses foot-pounds (ft-lb). Understanding the conversion between these units is essential for accurate calculations and engineering tasks.

Torque and Engine Performance

In automotive engineering, torque is a critical factor in evaluating engine performance. The engine’s ability to generate torque at various RPMs impacts a vehicle’s acceleration and towing capacity. Engineers and car enthusiasts often analyze torque curves to optimize engine design and performance.

Torque in Industrial Applications

Torque plays a vital role in industrial machinery and equipment. From conveyor belts to rotating turbines, understanding torque helps engineers design efficient systems that can handle specific workloads. We’ll explore practical examples of torque calculations in industrial settings.

Calculating Torque in Gears and Pulleys

Gears and pulleys are common components in many mechanical systems. Calculating torque in gear and pulley systems is essential for proper design and operation. We’ll delve into the math behind these calculations, considering gear ratios and the number of teeth in the gears.

Torque and Power Transmission

In mechanical systems, torque is closely related to power transmission. Understanding this relationship is essential for designing systems that efficiently transfer power from one component to another. We’ll explore various mechanical power transmission mechanisms and how to calculate torque in each scenario.

Torque and Bolt Tightening

In engineering and construction, properly tightening bolts is crucial to ensure structural integrity and safety. Torque is used to measure the force applied to tighten bolts accurately. We’ll discuss the importance of torque wrenches and how to calculate the required torque for different bolt sizes.

Torque and Electric Motors

Electric motors are prevalent in modern machinery and appliances. Understanding torque is essential for motor design and efficiency. We’ll explore how torque affects the performance and power consumption of electric motors.

Torque and Robotics

In the field of robotics, torque plays a significant role in designing robot arms and joints. Calculating torque in robot components helps ensure smooth and precise movements, making robots more capable of performing complex tasks.

Calculating Torque in Fluid Mechanics

Fluid mechanics involves the study of fluids in motion. Calculating torque in fluid dynamics is essential for understanding the behavior of rotating bodies in a fluid medium, such as propellers or turbines.

Measuring Torque: Torque Sensors and Dynamometers

Torque measurement requires accurate sensors and devices known as dynamometers. We’ll explore different types of torque sensors and how dynamometers work to measure torque in real-world applications.

The Role of Torque in Aerospace Engineering

In aerospace engineering, torque is a critical consideration when designing aircraft and spacecraft components. From the movement of control surfaces to the rotation of spacecraft in space, understanding torque is essential for successful missions.

Torque and Static Equilibrium

In physics, the concept of static equilibrium involves balancing forces and torques. Understanding torque is crucial for solving problems related to static equilibrium, such as determining the forces acting on a stationary object.

20 Examples of Torque

Here are 20 examples of torque:

  1. Turning a Doorknob: Applying torque to open or close a door.
  2. Pedaling a Bicycle: Torque from your legs makes the wheels turn.
  3. Twisting a Jar Lid: Torque helps you open stubborn jars.
  4. Tightening a Bolt: Using a wrench applies torque to secure bolts.
  5. Steering a Car: Turning the steering wheel involves torque.
  6. Using a Screwdriver: Turning a screw applies torque to drive it in or out.
  7. Operating a Faucet: Twisting the handle applies torque to control water flow.
  8. Riding a Skateboard: Shifting your weight applies torque for turns.
  9. Swinging a Bat: Torque helps in hitting a ball in baseball.
  10. Windmill Rotation: Wind applying torque to turn windmill blades.
  11. Opening a Water Bottle: Unscrewing the cap involves applying torque.
  12. Turning a Key in a Lock: Applying torque to unlock or lock doors.
  13. Using Pliers: Gripping and turning with pliers applies torque.
  14. Operating a Wrench: Tightening or loosening nuts with a wrench.
  15. Turning a Steering Wheel: In a boat or vehicle, torque directs movement.
  16. Adjusting a Bike Brake: Applying torque to adjust brake tension.
  17. Operating a Screw Jack: Torque is applied to lift heavy loads.
  18. Using a Hand Drill: Rotating the handle applies torque for drilling.
  19. Using a Crowbar: Applying torque to pry or lift objects.
  20. Turning a Wheelbarrow Handle: Moving and steering the wheelbarrow involves torque.


Q: What is the SI unit of torque?

A: The SI unit of torque is newton-meters (Nm).

Q: How does torque differ from force?

A: While both torque and force involve the application of a force, torque specifically deals with rotational forces, whereas force is a linear concept.

Q: Can torque be negative?

A: Yes, torque can be negative when the applied force creates a rotational motion in the opposite direction.

Q: What are some real-world examples of torque?

A: Examples of torque in real-world scenarios include tightening screws, operating a wrench, propelling vehicles, and rotating machinery.

Q: How do I convert torque units from newton-meters (Nm) to foot-pounds (ft-lb)?

A: To convert torque from newton-meters to foot-pounds, use the conversion factor: 1 Nm = 0.7376 ft-lb.

Q: What factors affect the torque produced by a machine?

A: The factors influencing torque include the applied force magnitude, the distance from the axis of rotation, and the angle between the force and the lever arm.