Question

An object whose mass is 100 lb falls freely under the influence of gravity from an initial elevation of 600 ft above the surface of earth. The initial velocity is downward with a magnitude of50 ft/s. The effect of air resistance is negligible. Determine the velocity, in ft/s, of the object just before it strikes earth. Assumeg= 31.5 ft/s2

Answer 1

Initial speed of drop is given by

$v_i = 50 ft/s$

total displacement of the object from top

$d = 600 ft$

acceleration due to gravity

$a = 31.5 ft/s^2$

so the final speed is given by kinematics equation

$v_f^2 - v_i^2 = 2 a d$

$v_f^2 - 50^2 = 2 * 31.5 * 600$

$v_f^2 - 2500 = 37800$

$v_f^2 = 40300$

$v_f = 200.7 ft/s$

so if will hit the surface at speed 200.7 ft/s