1-D motion homework help

Question

A rescue helicopter is hovering over a woman whose boat has sunk. One of the rescuers tosses a life preserver straight down to the woman with an initial speed of 1.45m/s and notices that it takes 1 5 sec to reach the water. How high above the water was the preserver released? Note that the downdraft of the helicopter reduces the effect of air resistance on the falling life preserver, so that an acceleration equal to that due to gravity is reason.

Answer 1

I would always start these problems by listing your "knowns"

1. t = 1.5 s
2. v_i = 1.45 m/s
3. a = g = 9.8 m/s²

And your unknown is d.

1. So you need a formula that includes d, a, v_i, and t
2. The formula cannot include other variables (but it could, in theory, include fewer variables, as long as there's a d)
3. d = v_i * t + 1/2 * a * t²
4. As long as you plug in correctly, you'll find your answer.