Problem 4-11 - Free fall - Part 11 - (B)
A ball is thrown from a balloon with an initial unknown velocity. The ball accelerates at \(9.80\;m/s^2\) downward for \(2.00\; s\), at which time its instantaneous velocity is \(24.0\; m/s\) at an angle of \(45.0^\circ\) below the horizontal. Determine the magnitude and direction of the initial velocity.
Accumulated Solution
\(v = v_0 + at\)
\(v_x = v_{0x} + a_xt \\ v_y = v_{0y} + a_yt \\ a_x = 0 \\ a_y = g \\ v_x = v_{0x} \\ v_y = v_{0y} + 9.8t \\ v_x = 24 \cos45 = 17.0\; m/s \\ v_y = 24 \cos45 = 17.0\; m/s \\ v_{0x} = v_{0x} = 17.0 \; m/s \\ v_{0y} = -2.6 \; m/s \\ v_0 = 17.2 \; m/s\)
Correct.
\(\theta\) is given by:
(A) \(\tan^{-1} |v_y|/|v_x|\)
(B) \(\tan^{-1} |v_x|/|v_y|\)
(C) \(\cos^{-1} |v_y|/|v_x|\)
(D) \(\sin^{-1} |v_x|/|v_y|\)