What force acts upwards to balance the weight of an aircraft?

• Gravity

• Thrust

• Lift

• Drag

Answer explanation

Lift is the upward force generated by the wings of an aircraft as air flows over them, counteracting the downward force of gravity and allowing the aircraft to ascend and maintain flight.

According to Bernoulli's principle, what happens when fluid velocity increases?

• Pressure increases

• Pressure decreases

• Temperature increases

• Temperature decreases

Answer explanation

According to Bernoulli's principle, as fluid velocity increases, the pressure within the fluid decreases. This inverse relationship is fundamental in fluid dynamics, making 'Pressure decreases' the correct answer.

What is the primary function of thrust in an aircraft?

• To overcome drag

• To increase weight

• To increase drag

• To decrease lift

Answer explanation

The primary function of thrust in an aircraft is to overcome drag, which opposes the aircraft's forward motion. Without sufficient thrust, the aircraft cannot maintain speed or altitude.

Which principle explains that for every action, there is an equal and opposite reaction?

• Newton's third law

• Coanda effect

• Newton's first law

• Bernoulli's principle

Answer explanation

Newton's third law states that for every action, there is an equal and opposite reaction. This principle explains how forces work in pairs, making it the correct choice for the question.

What is the effect of the 'Coanda effect' on airflow over a wing?

• Airflow follows a curved surface

• Airflow decreases velocity

• Airflow increases pressure

• Airflow separates from the wing

Answer explanation

The Coanda effect causes airflow to adhere to the curved surface of a wing, allowing it to follow the shape of the wing. This is crucial for generating lift, making 'Airflow follows a curved surface' the correct choice.

What happens to the air pressure on the top surface of a wing during flight?

• It fluctuates

• It increases

• It decreases

• It remains constant

Answer explanation

During flight, the air pressure on the top surface of a wing decreases due to the wing's shape and angle of attack, which causes air to move faster over the top, creating lower pressure compared to the bottom surface.

What is the relationship between thrust and drag for constant airspeed?

• Thrust equals drag

• Thrust is less than drag

• Thrust is unrelated to drag

• Thrust is greater than drag

Answer explanation

For constant airspeed, thrust must equal drag to maintain equilibrium. If thrust were greater, the aircraft would accelerate, and if less, it would decelerate. Thus, the correct relationship is that thrust equals drag.

What is the result when lift equals weight in an aircraft?

• The aircraft accelerates

• The aircraft climbs

• The aircraft descends

• The aircraft maintains level flight

Answer explanation

When lift equals weight, the forces are balanced, resulting in no vertical acceleration. Therefore, the aircraft maintains level flight.

What is the primary factor that determines the amount of lift and drag on a wing?

• The color of the wing

• The speed of the wing through the air

• The altitude of the wing

• The temperature of the air

Answer explanation

The primary factor determining lift and drag on a wing is the speed of the wing through the air. Higher speeds increase airflow, enhancing lift and drag effects, while other factors like color, altitude, and temperature have minimal impact.

What happens to lift when an aircraft increases its angle of attack?

• Lift becomes zero

• Lift increases

• Lift remains constant

• Lift decreases

Answer explanation

When an aircraft increases its angle of attack, the airflow over the wings changes, resulting in an increase in lift until a critical angle is reached. Therefore, the correct answer is that lift increases.