The height (in meters) of a shot cannonball follows a trajectory given by h(t)=−4.9t2+14t−0.4 at time t (in seconds). As an improper fraction, for how long is the cannonball above a height of 6 meters?
+29 maybe just set this function equal to 6 and solve for t, the result will be two cases.
t1 nearly equal 0.57s
t2 nearly equal 2.29s
hope it can help :)
+130477 6 = -4/9t^2 + 14t - 0.4 rearrange as
4.9t^2 - 14t + 6.4 = 0 multiply through by 10
49t^2 - 140t + 64 = 0 factor
(7t - 4) ( 7t - 16) = 0
Set each factor to 0 and solve for t and we have that
t = 4/7 sec and t = 16/7 sec
So.....the time it is above 6 m is
(16/7) - (4/7) =
12/ 7 sec
