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hamadehassan
17.10.2020 •
Mathematics
A rocket is launched straight up from the side of a cliff 40m high. If the initial velocity (v) is 30 m/sec and the height (H) is given by the formula = −16² + + ℎ, find the time at which the rocket will hit the ground. *
plsss help again :>>
A. 2.78sec
B. -0.90sec
C. 3.1sec
D.-0.6sec
Solved
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Ответ:
The time that the rocket will hit the ground is after 2.78 seconds.
Step-by-step explanation:
You know that the height (H) is given by the formula H= −16*t² + v*t+ h
A rocket is launched directly from the side of a 40 m high cliff and that the initial velocity is 30 m / sec. So this indicates that the value of v is 30 m / sec and h is the height of 40 m. Replacing this value in the formula you get:
H= −16*t² + 30*t+ 40
You must find the moment when the rocket will hit the ground, that is, the moment when the height H is zero:
0= −16*t² + 30*t+ 40
To calculate the time t the expression is used:
Being the general quadratic equation ax² + bx + c = 0, in this case a=-16, b=30 and c= 40. Replacing:
Solving:
Then:
Solving for t1:
t1=-0.9
Solving for t2:
t2=2.78
Since the time cannot be negative, the time that the rocket will hit the ground is after 2.78 seconds.
Ответ: