Small Gas Engines Chapter 6 Test

The horsepower correction factor is a figure that is used to adjust the brake horsepower rating when the test conditions deviate from the standard conditions. It takes into account the variations in temperature, pressure, and humidity. By multiplying the temperature correction, pressure correction, and humidity correction factors, the correction factor is calculated. This correction factor is then applied to the measured horsepower to obtain the corrected brake horsepower rating.

Indicated horsepower (ihp) is a measure of the power developed by the burning fuel mixture within the cylinder. It represents the power output of an engine based on the pressure measurements taken within the cylinder during the combustion process. This measurement helps to assess the efficiency and performance of the engine by providing an indication of how effectively the fuel is being burned and converted into power. It is not related to measuring the horsepower of the engine based on the radius of the tires or any other factor.

The text discusses one and two cylinder piston engines.

Centripetal force is the force that acts opposite to the direction of centrifugal force. Centrifugal force is the apparent force that pushes objects away from the center of rotation, while centripetal force is the actual force that pulls objects towards the center of rotation, keeping them in circular motion. Without the presence of centripetal force, objects would move in a straight line tangent to the circular path. Therefore, centripetal force is the correct answer as it counteracts the centrifugal force.

The force applied opposite to the way a compressive force is applied is called tensile strength. Tensile strength refers to the ability of a material to resist being pulled apart or stretched. It is the resistance to tension or pulling forces. Muscle strength and torque strength are not specifically related to opposing compressive forces.

The rated horsepower of an engine is the amount of power it can consistently produce under normal operating conditions. It is typically lower than the maximum brake horsepower, which is the highest amount of power the engine can produce in short bursts. Therefore, the rated horsepower is a percentage of the maximum brake horsepower, and in this case, it is approximately 80% of the maximum brake horsepower.

The Prony brake is a device used to measure the power output of an engine. In this case, a Prony brake with a 12" arm is applied to the engine flywheel. At 1200 rpm, the scale registers 20 lb. To calculate the horsepower, we use the formula: horsepower = (rpm x torque) / 5252. In this case, the rpm is 1200 and the torque is 20 lb. Plugging these values into the formula, we get: horsepower = (1200 x 20) / 5252 = 4.52 hp. Therefore, the correct answer is 4.52 hp.

The pressure is calculated by dividing the force applied (35 lb) by the area over which the force is applied (5 sq in). Therefore, the pressure is 7 psi.

The amount of power exerted is calculated by multiplying the force (60 lb) by the distance (5 ft) and dividing by the time (6 sec). This gives us (5 ft X 60 lb/6 sec) which simplifies to 50 ft-lb per sec.

The correct answer is 3 1/2%. This means that for every 1000 feet of elevation, the engine horsepower is reduced by 3 1/2%. This reduction is due to the decrease in air density at higher altitudes, which affects the combustion process in the engine. As a result, the engine produces less power, leading to a decrease in horsepower.

The formula for work is given by multiplying the force applied to an object by the distance over which the force is applied. This equation represents the concept that work is done when a force is exerted on an object and it moves in the direction of the force. The formula W = F x d quantifies the amount of work done, where W represents work, F represents force, and d represents distance.

The correct answer is 20-25%. This percentage represents the average amount of energy from fuel that is actually used to produce power. The rest of the energy is typically lost as waste heat. This range is considered to be relatively efficient, as it indicates that a significant portion of the energy is being converted into usable power.

To compute engine displacement, you need to determine the circular area of a cylinder and then multiply this figure by the stroke of the piston. Engine displacement refers to the total volume swept by all the pistons in the cylinders of an engine during one complete revolution. The circular area of a cylinder represents the cross-sectional area of the cylinder bore, and multiplying it by the stroke of the piston gives you the total volume displaced by the piston as it moves up and down within the cylinder. This calculation helps determine the engine's size and performance characteristics.

The correct answer explains that horsepower is the rate at which power is developed and that one horsepower is the ability to lift 550 pounds, 1 foot in 1 second. This definition accurately describes the concept of horsepower, which is commonly used to measure the power output of engines, particularly in the automotive industry.

The standard test conditions for testing an engine on the dynamometer are air dry, temperature at 60 degrees F, and barometric pressure of 29.92 inches of mercury (Hg). These conditions ensure that the engine is tested under consistent and controlled environmental factors, allowing for accurate and comparable results. The temperature and barometric pressure are specified to eliminate any variations that could affect the engine's performance, while the air dry condition ensures that the air entering the engine is free from moisture, which could also impact its performance.

Brake horsepower is the correct answer because it refers to the measure of horsepower delivered at the engine crankshaft. This term specifically indicates the power output of an engine without any losses from the transmission, clutch, or other components. It represents the actual power available for performing work and is commonly used to rate the power of engines in automotive and industrial applications.

The statement is false because the horsepower of an engine is not always greatest at maximum rpm. Horsepower is a measure of the engine's power output, and it can vary at different rpm levels. While some engines may reach their peak horsepower at or near the maximum rpm, others may have a different rpm range where they produce the highest horsepower. Therefore, it is not accurate to say that the horsepower of an engine is always greatest at maximum rpm.

The correct answer is 4.91 sq. in (D squared X 0.7854). This is because the formula for finding the area of a circle is A = πr^2, where A is the area and r is the radius. In this case, the diameter of the piston is given as 2 1/2", which is equivalent to a radius of 1 1/4". Plugging this value into the formula, we get A = π(1 1/4)^2 = 3.1416(1.25)^2 = 3.1416(1.5625) = 4.91 sq. in.

Volumetric efficiency refers to the ability of an engine to efficiently intake and exhaust air. At higher speeds, such as 1800 rpm, the engine is able to intake and exhaust air more effectively, resulting in a greater volumetric efficiency. This is because the higher speed allows for more air to be drawn into the engine, leading to improved combustion and overall performance.

When an object is raised 3' and then moved 5' sideways at the same level, the work is only being done over the vertical distance of 3'. The horizontal movement does not require any work to be done as there is no change in height. Therefore, the correct answer is 3'.