Solve the problem.
-A ball is thrown upward with an initial velocity of 21 meters per second from a cliff that is 100 meters high. The height of the ball is given by the quadratic equationquation $h = - 4.9 t ^ { 2 } + 21 t + 150$ where h is in meters and t is the time In seconds since the ball was thrown. Find the time that the ball will be 50 meters from the ground. Round your Answer to the nearest tenth of a second.
A)8.2 seconds
B)7.2 seconds
C)7.1 seconds
D)8.1 seconds

Question

Quizplus · Accepted Answer

To find the time when the ball is 50 meters from the ground, set $h = 50$ in the given equation and solve for $t$: $50 = -4.9t^2 + 21t + 100$. Rearranging gives $4.9t^2 - 21t + 50 = 0$. Solving this quadratic equation for $t$ gives two solutions, but the one that makes physical sense in this context (considering the ball is thrown upwards and then falls down) is approximately $t = 7.1$ seconds.

Solve the Problem h=−4.9t2+21t+150h = - 4.9 t ^ { 2 } + 21 t + 150h=−4.9t2+21t+150

Solve the Problem $h = - 4.9 t ^ { 2 } + 21 t + 150$