h(t) = - 18 t² + 72 t + 378
The piece of debris hit the ground when h = 0
h(t) = - 18 t² + 72 t + 378 = 0
Now you must solve equation:
- 18 t² + 72 t + 378 = 0
The solutions are:
t = - 3 and t = 7
Time cannot be negative.
So t = 7 sec
An explosives company specializes in bringing down old buildings. The time it takes for a particular piece of flying debris to fall to the ground can be modelled by the function h left parenthesis t right parenthesis equals negative 18 t squared plus 72 t plus 378, where h is the height of the debris, in metres, and t is the time, in seconds.
How long will it take for the piece of debris to hit the ground after an explosion?
1 answer