Horsepower Formula

We sure use a lot of machinery in our daily lives. From refrigerators to water purifiers, bikes and scooters to buses and trucks, etc. To measure the output of engines in motor vehicles, horsepower is an efficient unit. 

What is Horsepower?

Horsepower is a common imperial measurement of engine power. It is the quantity of work completed by a human or machine in a given length of time. James Watt was the one who coined the term “horsepower.” It is a measure of power that compares the muscle power of a horse to the power of a machine. One horsepower consists of approximately 750 W.

It was originally used to compare the output of steam engines to the strength of draught horses. However, its use was gradually broadened to include many types of pistons, gas turbines, compressors, and other equipment.

Basic Terminology

In order to understand the formula for horsepower, we need to understand the following two terms:

• Torque: The force that may cause an item to twist along an axis is measured as torque. In linear kinematics, pressure is what enables an article to accelerate. Torque is also responsible for the angular acceleration. As a result, torque may be defined as the linear force’s rotational equivalent. The axis of rotation is the point at which the item rotates.

• RPM: RPM stands for Revolutions Per Minute in its complete form. It’s a computation of an object’s rotation frequency, or how many revolutions or turns it makes every minute. It depicted how many times an involuntary component rotates around its axis in a minute. The rotating frequency or speed of rotation of an uncontrolled entity along a fixed axis, such as a driveshaft, a turbine powerplant, a DVD or CD player, or a turbocharger, is therefore defined as RPM.

Formula

Horsepower = Torque x Speed/5252 

or

Horsepower = 

Sample Problems

Question 1. A car moves at 300 RPM with a 50 ft – lbf of torque. Find its horsepower.

Solution:

Given: Torque = 50 ft – lbf, Speed = 300 RPM

Since, Horsepower = Torque x Speed/5252

= 50 x 300/5252

= 15000/5252

Horsepower = 2.856 HP

Question 2. Find the horsepower of an object with torque and speed of 120 ft- lbf and 5900 RPM. 

Solution:

Given: Torque = 120 ft – lbf, Speed = 5900 RPM

Since, Horsepower = Torque x Speed/5252

= 120 x 5900/5252

= 708000/5252

Horsepower = 134.805 HP

Question 3. Find the horsepower of an object with torque and speed of 69 ft- lbf and 420 RPM. 

Solution:

Given: Torque = 69 ft – lbf, Speed = 420 RPM

Since, Horsepower = Torque x Speed/5252

= 69 x 420/5252

Horsepower = 5.517 HP

Question 4. Find the horsepower of an object with torque and speed of 420 ft- lbf and 1000 RPM. 

Solution:

Given: Torque = 420 ft – lbf, Speed = 1000 RPM

Since, Horsepower = Torque x Speed/5252

= 420 x 1000/5252

Horsepower = 79.969 HP

Question 5. Find the horsepower of an object with torque and speed of 900 ft- lbf and 500 RPM. 

Solution:

Given: Torque = 900 ft – lbf, Speed = 500 RPM

Since, Horsepower = Torque x Speed/5252

= 900 x 500/5252

Horsepower = 85.681 HP

Question 6. Find the horsepower of an object with torque and speed of 70 ft- lbf and 80 RPM. 

Solution:

Given: Torque = 70 ft – lbf, Speed = 80 RPM

Since, Horsepower = Torque x Speed/5252

= 70 x 80/5252

Horsepower = 1.066 HP

Question 7. Find the horsepower of an object with torque and speed of 44 ft- lbf and 33 RPM. 

Solution:

Given: Torque = 44 ft – lbf, Speed = 33 RPM

Since, Horsepower = Torque x Speed/5252

= 44 x 33/5252

Horsepower = 0.276 HP