There are only two forces acting on a glider: an aerodynamic force and a gravitational force. The gravitational force is directed towards the center of the earth and is equal to the product of mass m and gravitational acceleration g.
The aerodynamic force is usually represented by its two components: the drag force D acting opposite to the direction of movement, and the lift force L perpendicular to it.
For a glider moving at constant altitude the lift force is equal to the gravitational force: L = m * g ... (equation 1)
There is no force opposing the drag force so according to Newton's second law there results an acceleration a resulting from the equation: - D = m * a ... (equation 2)
(The sign convention is positive for forces and accelerations in the direction of motion, negative in the opposite direction)
Combining equations (1) and (2) we get: a / g = - D / L
No need to discuss momentum or energy.
P.S. If you measure accelerations in kts/second, then g is about 19.05 kts/second
Last edited by HazelNuts39; 25th Nov 2012 at 16:09.
Reason: P.S.