Question

An object is thrown in the air with an initial velocity of 5 m/s from a height of 9 m. The equation h(t) = –4.9t2 + 5t + 9 models the height of the object in meters after t seconds. About how many seconds does it take for the object to hit the ground? Round your answer to the nearest hundredth of a second. Question 11 options: 0.94 seconds 1.50 seconds 2.00 seconds 9.00 seconds

Answer 1

On a graph, x axis is time and y axis is height. Set equation equal to zero to find x-intercept because this is when h=0
x = 1.9583211, -0.9379.....
time cannot be negative therefore it hits the ground after 2.00s

n.b. This is a very hard equation to factorise, so either a graphics calculator or computer program will help with this one.