## anonymous one year ago Sandra throws an object into the air with an initial vertical velocity of 38 ft/s, from a platform that is 30 ft above the ground. How long will it take the object to hit the ground? A. 2 s B. 3 s C. 1 s D. 4 s

1. jdoe0001

hint: $$\bf \text{initial velocity}\\ h = -16t^2+v_ot+h_o \qquad \text{in feet}\\ \\ \quad \\ v_o=\textit{initial velocity of the object}\\ h_o=\textit{initial height of the object}\\ h=\textit{height of the object at "t" seconds}$$

2. jdoe0001

you're given $$bf v_o\ and \ h_o$$ thus use them, plug them in keep in mind that, that the object hits the ground when y = 0

3. jdoe0001

anyhow $$\bf v_o\ and \ h_o$$ are given

4. jdoe0001

|dw:1437610147955:dw| thus $$\bf \text{initial velocity}\\ h = -16t^2+v_ot+h_o \qquad \text{in feet}\\ \\ \quad \\ v_o=38\\ h_o=30\\ \\ \quad \\ h = -16t^2+38t+30\qquad \textit{hits the ground}\to {\color{brown}{ 0}} = -16t^2+38t+30$$

5. anonymous

i;m thinking B then

6. jdoe0001

because?

7. jdoe0001

why not just solve it for "t"?

8. anonymous

ohhh so its A ok

9. anonymous

no its acctually C

10. anonymous

yes it is

11. anonymous

C