v = Vi - g t
h = hi + Vi t - 4.9 t^2
after 3 seconds
h = 40 + 10 (3) - 4.9*9
= 25.9 meters above ground on the way down
0 = 40 + 10 t - 4.9 t^2
4.9 t^2 - 10 t - 40 = 0
t = [ 10 +/- sqrt(100 +784) ] / 9.8
take big t choice (on the way down)
t = 4.05 seconds
Yoko threw a stone upward at a speed of 10m/sec while standing on a cliff 40 m above ground.
A. What was the height of the stone after 3 seconds?
B. Estimate how long it took for the stone to touch the ground
1 answer