Question

The height in meters of a projectile can be modeled by h = -4.9t2 + vt + s where t is the time (in seconds) the object has been in the air, v is the initial velocity (in meters per seconds) and s is the initial height (in meters). A soccer ball is kicked upward from the ground and flies through the air with an initial vertical velocity of 4.9 meters per second. After how many seconds does it land approximately?

Answer 1

When it lands, it height (h) will be zero. so 0=-4.9t^2 + vt + s. It starts off the ground, so s= 0 and its initial velocity is 4.9 m/s, so the equation is now 0 = -4.9t^2 + 4.9t. solve for t.

Answer 2

^^v= 4.9

Answer 3

0 = t(-4.9t +4.9)
so t = 0 and 1
we can ignore the zero since it is the instant we kicked the ball off the ground, so the answer is that after 1 second, the ball touches the ground.