I need help solving 69, 71, 72, 74, and 75. Please show work when solving the problems. Thank you!

69. Explain why an aluminum ball and a steel ball of similar size and shape, dropped from the same height, reach the ground at the same time. 70. Give some examples of falling objects for which air resistance can and cannot be ignored. Mastering Problems 71. Suppose an astronaut drops a feather from a height of 1.2 m above the surface of the Moon. If the free- fall acceleration on the Moon is 1.62 m/s2 downward, how long does it take the feather to hit the Moon's surface? toside owls 72. A stone that starts at rest is in free fall for 8.0 s. a. Calculate the stone's velocity after 8.0 s. b. What is the stone's displacement during this time? 73. A bag is dropped from a hovering helicopter. The bag has fallen for 2.0 s. What is the bag's velocity? How far has the bag fallen? Ignore air resistance. 74. You throw a ball downward from a window at a speed of 2.0 m/s. How fast will it be moving when it hits the sidewalk 2.5 m below? 75. If you throw the ball in the previous problem up instead of down, how fast will it be moving when it hits the sidewalk