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

Question

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

jdoe0001 · Answer

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}$

jdoe0001 · Answer

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

jdoe0001 · Answer

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

jdoe0001 · Answer

|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$

anonymous · Answer

i;m thinking B then

jdoe0001 · Answer

because?

jdoe0001 · Answer

why not just solve it for "t"?