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?

Question

2 months ago

5

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 answer was 6 m/s 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?
a.yes, the obtained speed is less than the world-record.
b.yes, the obtained speed is almost equal to the world-record.
c.no, the obtained speed is greater than the world-record.
d.no, the obtained speed is almost equal to the world-record.

Physics

2 answers:

Ostrovityanka [3.2K] · Answer 1 · 2026-02-17T03:21:32+03:00

Part (a): Brady must achieve a minimum speed of $\boxed{6\text{ m/s}}$ to make the jump across the river.

Part (b): Brady’s leap speed is feasible since it is below the world record speed.

Further details:

(a)

Brady attempts to jump a horizontal span of $22\text{ ft}$ from a height of $20\text{ft}$ , obeying Newtonian motion laws.

Given:

Horizontal distance: $22\text{ ft}$

Vertical height: $20\text{ft}$

Concept:

The horizontal measurement in meters is $6.71\text{ m}$ .

The vertical measurement in meters is $6.10\text{ m}$ .

The time of flight is calculated using the equation of motion:

$s=ut+\dfrac{1}{2}at^2$

Replacing $0\text {m/s}$ with $u$ and rearranging to solve for $t$ :

$t=\sqrt{\dfrac{2s}{a} }$

Substitute values: $6.10\text{ m}$ for $s$ and $9.81\text{ m}/\text{s}^2$ for $a$ in the equation.

$\begin{aligned}t&=\sqrt{\dfrac{2\times6.10}{9.81}}\text{ s}\\&=1.12\text{ s}\end{aligned}$

The flight time equals the duration to cover the horizontal distance.

Brady’s horizontal velocity is:

$\begin{aligned}v&=\dfrac{6.71}{1.12}\text{ m/s}\\&\approx6\text{ m/s}\end{aligned}$

Therefore, Brady’s minimum speed must be $\boxed{6\text{ m/s}}$ to cross successfully.

(b)

The minimum speed Brady must run at is $6\text{ m/s}$ .

The world record speed is:

$\begin{aligned}V&=\frac{100}{10}\text{ m/s}\\&=10\text{ m/s}\end{aligned}$

Thus, Brady’s required speed is achievable because it remains below the world record.

Keith_Richards [3.2K] · Answer 2 · 2026-02-17T03:23:09+03:00

Answer:

A. Yes, because the calculated speed is below the world record

Explanation:

The speed obtained is 6 m/s.

World record speed is distance over time: 100 m divided by 10 s equals 10 m/s.

Consequently, the required speed is less than the record speed.

Not only is it less, but this speed is a reasonable estimate for an athletic individual's average pace, making the jump feasible.

-Samuel Brady became famous for his leap over the Cuyahoga River near Kent, Ohio around 1780. Pursued by a group of Indians after an unsuccessful ambush, he escaped by jumping across a 22-foot (6.7 m) wide section of the river (which was expanded in the 1830s for canal construction). He then hid underwater using a reed for breathing by a fallen tree near a lake.