SAT Subject Physics Practice Question 517: Answer and Explanation

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Question: 517

3. Firefighters attempt to squirt water from a hose into a third story window 15 m above the ground. For safety purposes they stand 25 m from the burning building. The water from the hose can only reach the window if

A. ty > tx
B. tx > ty
C. ty < tx
D. tx < ty
E. Time has no effect in this case.

Correct Answer: C


The correct answer is (C). The time an object moves along the x-axis while it is also moving in free fall on the y-axis is restricted to the time the object is in free fall. The water from the fireman's hose must be in free fall at least long enough to reach the height at which the window is located above ground and cross the distance from the hose to the burning building, too. This means that at the very least, the time the water rises (ty) must equal the time the water takes to move from the hose and cross the street on the x-axis (tx).

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