In 1780, in what is now referred to as "Brady's Leap," Captain Sam Brady of the U. S. Continental Army escaped certain death from his enemies by running over the edge of the cliff above Ohio's Cuyahoga River in (Figure 1), which is confined at that spot to a gorge. He landed safely on the far side of the river. It was reported that he leapt 22 ft (≈ 6.7 m) across while falling 20 ft (≈ 6.1 m).

What is the minimum speed with which he'd need to run off the edge of the cliff to make it safely to the far side of the river?

Express your answer to two significant figures and include the appropriate units.

Question

Physics

Jett

26 January, 21:48

In 1780, in what is now referred to as "Brady's Leap," Captain Sam Brady of the U. S. Continental Army escaped certain death from his enemies by running over the edge of the cliff above Ohio's Cuyahoga River in (Figure 1), which is confined at that spot to a gorge. He landed safely on the far side of the river. It was reported that he leapt 22 ft (≈ 6.7 m) across while falling 20 ft (≈ 6.1 m).

What is the minimum speed with which he'd need to run off the edge of the cliff to make it safely to the far side of the river?

Express your answer to two significant figures and include the appropriate units.

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Answers (1)

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Kara Lyons · Answer 1

While landing on free-fall, the distance travelled can be expressed as d = (1/2) (g) (t²). Thus, we have 6.1 = (1/2) (9.8) (t²) t² = 2 (6.1) / 9.8 t = √ [ (2) (6.1) / 9.8] To look for the speed needed to cover the distance of 6.7 m, we have v = d/t = 6.7 / √ [ (2) (6.1) / 9.8] v ≈ 6.0 m Therefore, the minimum speed needed, estimated to two significant figures, is 6.0 m.