Posted by kathryn on .
If an object is dropped from a tall building and hits the ground 3.0 s. later, what is the magnitude of the object's displacement in 1.0 s.; in 2.0 s.?
for 1.0s i got 9.8
for 2.0s i got 20.
is this correct?

physics 
Steve,
doesn't matter how long it takes to hit the ground.
s = 1/2 at^2 = 4.9t^2
s(1) = 4.9
s(2) = 19.6
How did you get 9.8 for s(1)? Curious, since you got s(2) correct. Ah. you must have used 9.8t, rather than 4.9t^2.
The speed is 9.8t. Better review those formulas some more.