- An experienced pilot can keep an engineless glider aircraft aloft for hours by using only the lift provided by rising air currents. Suppose during a flight an
upward force of 5.00 103 N is exerted on the glider. Simultaneously, the
glider experiences a forward force of 0.50 103 N. The gravitational force
acting on the glider and its pilot is 4.80 10N. Draw a free-body diagram of
the glider.

Aparticle's position is given by x = 3.00 - 9.00t + 3t2, in which x is in meters and t is in seconds. (a) what is its velocity at t = 1 s? (b) is it moving in the positive or negative direction of x just then? (c) what is its speed just then? (d) is the speed increasing or decreasing just then? (try answering the next two questions without further calculation.) (e) is there ever an instant when the velocity is zero? if so, give the time t; if not, answer "0". (f) is there a time after t = 3 s when the particle is moving in the negative direction of x? if so, give the time t; if not, answer "0".