25. A punter kicks a football upward with an initial speed of 48 feet per second. After how many seconds does the ball hit the ground? Use the formula h = rt − 16t2 where h represents height in feet and r represents the initial speed.

Question

25.   A punter kicks a football upward with an initial speed of 48 feet per second. After how many seconds does the ball hit the ground? Use the formula h = rt − 16t2 where h represents height in feet and r represents the initial speed.

parthkohli · Answer

Ground means height of 0, right? So, think of this like this.

$ \color{Black}{\Rightarrow 0 = 48t - 16t^2 }$

parthkohli · Answer

Note that I have that 48 because initial speed is 48.

apoorvk · Answer

so, equate the equation of the height with zero, since the height of the ball becomes zero when it strikes the ground! and find 't' ofcourse.

anonymous · Answer

208?

parthkohli · Answer

This is a quadratic equation.

parthkohli · Answer

$ \color{Black}{\Rightarrow 0 = 16t(3 - t) }$

Use the zero product rule.

anonymous · Answer

then its 48t? right

anonymous · Answer

Im sorry i have no idea how to do this :(

parthkohli · Answer

$ \color{Black}{\Rightarrow 16t = 0 \text{ or } 3 - t = 0 }$

parthkohli · Answer

16t = 0
t = 0

Obviously it can't take 0 seconds, so solve for 3 - t = 0

anonymous · Answer

so the answer is 3-t=0?

apoorvk · Answer

yeah. so what's 't' then?

parthkohli · Answer

Yes, solve this further.

$ \color{Black}{\Rightarrow 3 - t = 0}$

Subtract 3 from both sides then multiply both sides by -1.

anonymous · Answer

Uggg i have no idea :\

parthkohli · Answer

$ \color{Black}{\Rightarrow -t = -3 }$

$ \color{Black}{\Rightarrow t = 3 }$

anonymous · Answer

so its 3.................

parthkohli · Answer

yep

anonymous · Answer

Lol thats what i got but i thought i was really wrong thanks tho! :p lol