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The Forces |
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Forces on a Plane:
 Photo by NASA: http://www.grc.nasa.gov/WWW/k-12/airplane/forces.html  Equ.
of Lift Equ.
of DragPhotos found at: http://web.mit.edu/16.00/www/aec/flight.html |
When an airplane travels through the air, four main forces
are constantly acting on it. These forces are: Lift, Drag,
Thrust, and Weight. Lift For an
airplane to fly, the lift generated by the air moving
over the wings must overcome the weight of the plane due
to gravity. How much lift that is generated depends on
the plane and the shape of the wings. The equation of
lift is used by engineers to determine the lift needed
for a plane when designing a wing. The higher the
Coefficient of Lift (CL) is the
better. In the equation S is the wing's area,
the values in parentheses is the dynamic
pressure with V being the velocity and rho being
the density of the air. (Equation bottom
left)
Drag: Drag is
produced when the air moving against the aircraft
resists it, pushing the plane back. This is usually
considered as air resistance. The magnitude of drag
varies depending on the shape of the plane and the
atmosphere that the plane is passing through. Along side
determining the lift, engineers use the equation of drag
to determine the drag made for the design of the
aircraft. The lower Coefficient of Drag (CD)
results in the least drag created. In the equation, A is
the cross-sectional area, the values in the parentheses
is the dynamic pressure with V
being the velocity and rho being the density of
the air. (Equation
bottom left)
Thrust: To overcome
drag, a force of thrust must be given by the engines on
an airplane to push it forward. Thrust can be considered
using Newtons second law of Force =
(mass)*(acceleration) where the mass and acceleration
are considering the air that is expelled by the engine. Weight: The weight
is the downward force of an object, which is calculated
by multiplying the mass of the object by the force of
gravity. This can be difficult to consider during flight
as when the plane tilts, the center of gravity changes.
This makes it difficult when calculating the other
forces as they are affected by the change. |