Question

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?  

The world-record time for the 100 m dash is approximately 10 s. Given this, is it reasonable to expect Brady to be able to run fast enough to achieve Brady's leap?

Answer 1

for Brady's leap

along vrtical

voy = 0

acceleration ay = -9.8 m/s^2

displacement y = -6.1 m

y = voy*t + (1/2)*ay*t^2

-6.1 = 0 - (1/2)*9.8*t^2

t = 1.12 s

along horizontal

velocity vx = v

displacement x = 6.7 m

acceleration ax = 0

x = vx*t + (1/2)*ax*t^2

6.7 = v*1.12

v = 6 m/s <<--------answer

for world record speed = 100/10 = 10 m/s

No