Horsepower vs Torque What is the Difference?

Do of you find physics fascinating? Does gravitation, momentum, torque or E=mc2  intrigue you? Is physics all you dream of? Well, if the answer is “yes to all” then embrace yourself because we’re about to go round and round with some heavy ‘Torque’. So, what exactly is the quantity Torque? What is the principle or working concept laying underneath it? Also, how does it differ from horsepower? These are the several questions that we will try to answer in this article.

‘Torque’ defined:

It is the measure of a force, acting directly on an object, causing the object to rotate. You’ve probably heard of the terminology ‘torque’ often being associated with automobiles. So, in terms of an automobile, the force created by the pistons acts on the crankshaft, causing the wheels to rotate. It is a physical quantity and is very much a term associated with physics. It is more commonly known as the twisting force. The object which rotates due to application of torque rotates along an axis. This axis is commonly defined as the axis of rotation.

Torque is a quantity we all use in our everyday lives. The most common examples of application of Torque would be anything where we apply a force causing something to rotate whether it is a doorknob, a key or a door itself; torque is all around us. However there is a very beautiful working of physics behind it.

What really happens behind the curtains?

In order to be able to determine the magnitude of a linear force, we have to be able to calculate the mass and the magnitude of acceleration too. Although, there is one additional element or quantity involved with the calculation of torque acting on a body. It is the distance from the axis where the force acts. To sum it in simpler terms, think of pushing a door. You wouldn’t push a door close to the hinges, would you? That would make it very hard to open the door. So the distance from the hinges is the additional factor involved in this case.

Equation for calculating Torque:

T=F * r * sin (θ);

Where T= Torque, F= linear force, r=radial distance from axis, θ= angle between r and F.


Now, most of us have seen movies pertaining to cars. We certainly have come across this term ‘Horsepower’. Among car enthusiasts the higher the hp, more powerful is the car. So, let’s define it.

It is basically a unit of power and is used for expressing the quantity. Horsepower is used to tell the how fast mechanical energy is being spent. The power equivalent of 1hp is 746 watts which is further equal to 0.746 Kwatts.  

What differentiates Torque from Horsepower?

According to Layman, measurement of horsepower is only during high RPM while for Torque it is at much lower RPMs. Mathematically speaking, the power required to pull 550 pounds of load by 1 foot in just 1 second is called Horsepower. A dynamometer is generally used for the measurement of engine horsepower; however what the dynamometer really does is it introduces a load to the engines thus measuring the Torque. Horsepower is a measurement derived from torque due to the ease of measurement of the latter quantity.


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