SOLUTION: How would you set up the following word problem: You are hitting baseballs. When tossing the ball into the air, your hand is 5 feet above the ground. You hit the ball when it fa

How would you set up the following word problem: You are

hitting baseballs. When tossing the ball into the air, your

hand is 5 feet above the ground. You hit the ball when it 

falls back to a height of 4 ft. If you toss the ball with 

an initial velocity of 25ft/sec, how much time will pass 

before you hit the ball? Thanks!



Use the formula h = h0 + v0t - 16t2 since distance is given

in feet. (If distance were in meters, we would have to use

4.9 where the 16 is).



h0 represents the initial height. v0 represents the initial 

velocity, and h is height at the instant when t seconds have

elapsed.



>>...When tossing the ball into the air, your hand is 5 feet 

above the ground...<<



So h0 = 5



>>...you toss the ball with an initial velocity of 25ft/sec...<<



So v0 = 25



So we substitute 5 for h0 and 25 for v0, making our formula



h = 5 + 25t - 16t2



>>...You hit the ball when it falls back to a height of 4 ft...<<



So we wish to find t (the number of seconds) has elapsed at the

instant when the ball is 4 feet high, so we substitute 4 for h

and solve for t:



4 = 5 + 25t - 16t2



16t2 - 25t - 1 = 0



Use quadratic formula, get solutions  



-.04 and 1.6.  We ignore the negative answer.  So the answer is



1.6 seconds approximately.



Edwin