To determine the domain of the function \( H(t) = 400 - 16t^2 \), we need to consider the context of the problem:
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Physical Context: The function models the height of a ball dropped from a building. The ball will fall until it reaches the ground, which means its height \( H(t) \) will reach 0.
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Finding when the ball hits the ground: To find the time when the ball hits the ground, we set \( H(t) \) equal to 0 and solve for \( t \):
\[ 0 = 400 - 16t^2 \] \[ 16t^2 = 400 \] \[ t^2 = 25 \] \[ t = 5 \text{ seconds} \]
Since time cannot be negative in this context, we only consider \( t = 5 \).
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Domain: The ball is dropped at \( t = 0 \) seconds, and it hits the ground at \( t = 5 \) seconds. Thus, the time \( t \) can take any value from 0 to 5 seconds, inclusive.
In conclusion, the domain of the function \( H(t) = 400 - 16t^2 \) is:
\[ \text{Domain: } [0, 5] \]
This means \( t \) can range from 0 to 5 seconds.