Question

Your friend drops your house keys down to you from their second floor window. If you catch them 2.4 m from where your friend dropped them, what is the velocity of the keys when you catch them?

Answer 1

a.
-6.9 m/s
c.
-7.2 m/s
b.
-6.5 m/s
d.
-7.4 m/s

Answer 2

the keys are accelerating downwards at 9.8 m/s^2 but have no initial velocity (they were dropped not thrown). Always draw a diagram



\(y_i=2.4~ m\)
\(y_f=0~ m\)
\(v_i=0\)

use: \(v_f^2=v_i^2+2a\Delta x\)

\(v_f^2=(0)^2+2(-9.8~m/s^2)(0~m-2.4~ m)\)

\(v_f=\sqrt{47.04}=6.8585~m/s \approx 6.9~m/s\)