How long does it take an object to fall to a point 12 m below if it was thrown upward with a speed of 6 m/s?

The answer is 2.29 sec.





How did my teacher get this?How long does it take an object to fall to a point 12 m below if it was thrown upward with a speed of 6 m/s?
-12.6=-72How long does it take an object to fall to a point 12 m below if it was thrown upward with a speed of 6 m/s?
Do this in parts - constant accelerated motion


pt 1:


How long does it take for gravity (g) to diminish 6 m/s to 0.


(at zero speed the object has risen to its max height)


t1 = time to come to zero speed = 6/g = 6/9.8 = 0.61 sec





pt 2:


We know that under constant accelerated motion an object falls back to the same height it was launched from in the same time interval it took to rise. And at launch height it will have the same speed (although downward in direction) it had when launched.


So object takes another 0.61 sec to fall back to launch height.





pt 3:


The formula for distance under gravity with an initial velocity is:


d = v0(t) + 1/2gt虏


12 = 6t + 4.9t虏


0 = -12 + 6t + 4.9t虏


solve quadratic for + t


t = 1.07 sec





Add times from 3 pts:


Total time = 0.61 + 0.61 + 1.07 = 2.29 sec ANS

beauty treatments

car oil