(Solved): Q9 A ball is thrown straight up with a speed of \( 30 \mathrm{~m} / \mathrm{s} \), and air resistanc ...

A ball is thrown straight up with a speed of \( 30 \mathrm{~m} / \mathrm{s} \), and air resistance is negligible. What is its velocity after \( 4.2 \mathrm{~s} \) ? \( .71 \mathrm{~m} / \mathrm{s} \) \( -11 \mathrm{~m} / \mathrm{s} \) \( 71 \mathrm{~m} / \mathrm{s} \) \( 11 \mathrm{~m} / \mathrm{s} \)