Difference between Momentum and Torque

Key Difference: Torque (moment or moment of force), the word has been derived from Latin which means ‘to twist’. It is a tendency which measures the amount of force which acts upon a body in order to rotate it about a pivot or axis. Momentum is a property possessed by moving objects and is directly proportional to both mass and speed of the body. It can be described as a quantity which is associated with an object’s resistance to stopping.

Torque (moment or moment of force), the word has been derived from Latin which means ‘to twist’. It is a tendency which measures the amount of force which acts upon a body in order to rotate it about a pivot or axis. It is a vector quantity. If somebody pushes a door to open it,  the door rotates about its hinges. In this example, torque is being used. It can be referred to as the turning effectiveness of a force. The formula used for the calculation of torque is

T = r XF = rFsin(a)

 (It is a cross product between the distance vector (distance from pivot point to the point where the force is being applied) and the force vector) and a is the angle between r and F.

The direction of Torque is determined by using right hand rule – direct fingers towards r and then curl towards the direction of F. In this particular instance, the thumb will be pointing towards the direction of Torque. The SI unit of torque is a Newton-meter.

Momentum is another vector quantity. It is a property possessed by moving objects and is directly proportional to both mass and speed of the body. An object with a greater momentum is hard to stop than in comparison to an object with a lesser momentum. Thus, it can be described as a quantity which is associated with an object’s resistance to stopping. One can also refer to it as a type of moving inertia. The direction of momentum is the same as the velocity of the object.

Momentum =p=mv (mass * velocity)

The SI unit of momentum is kilogram meter per second. [kg m/s]

Torque can also be defined in terms of angular momentum as the rate of change of angular momentum.

Comparison between Momentum and Torque:

 

Momentum

Torque

Definition

It is a property possessed by moving objects and is directly proportional to both mass and speed of the body.

It is a tendency which measures the amount of force which acts upon a body in order to rotate it about a pivot or axis. It is a vector quantity.

Formula

Momentum =p=mv (mass * velocity)

 

T = r XF = rFsin(a)

 (It is a cross product between the distance vector (distance from pivot point to the point where the force is being applied) and the force vector) and a is the angle between r and F.

Direction

Same as the velocity of the object.

 

It is determined by using right hand rule

Unit

The SI unit of momentum is kilogram meter per second. [kg m/s]

Newton-meter

Properties

  • It is conserved when there are no external forces acting.
  •  It helps in understanding collisions.

 

  • It is calculated with respect to (about) a point.
  • A change in the point changes the magnitude and direction of the torque.

Image Courtesy: physics4kids.com, vexrobotics.com

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