Accelerated motion?

Question

Do equations for accelerated motion apply to freely falling bodies?

Answer 1

Yes. acceleration is due to unequal forces on a body. Gravity is such a force.

Answer 2

f = ma = W - Fd; where f = net force acting on a falling body with mass m weighing W = mg, where g = 9.81 m/sec^2 and being acted on by an upward drag force = Fd. Fd = 0 in a vacuum.

If the fall is in a vacuum, then f = ma = W - Fd = W; and ma = W = mg; so that a = g = W/m, the freely falling body will accelerate at g the acceleration due to gravity at Earth's surface.

But if the fall is in a gas (like air), then f = ma = W - Fd = mg - 1/2 Cd rho A v^2; where Cd = coefficient of drag friction, rho = air density, A = the cross sectional area of the body, and v = the body's velocity as it falls. Thus, ma = W - Fd and a = (W - Fd)/m < W/m, which shows that the acceleration with air will be less than it would be in a vacuum.

Further, when W = Fd (the drag force exactly offsets the weight of the body), we have a = (W - Fd)/m = 0/m = 0, and the body no longer accelerates. When this happens, we say the falling body has reached TERMINAL VELOCITY. The terminal velocity of an adult human is somewhere around 120 mph. give or take ten or so mph.

Answer 3

yes...definately