Height of a Cliff (Only time Given)

  • Thread starter Thread starter PhysGoat
  • Start date Start date
  • Tags Tags
    Height Time
Click For Summary
SUMMARY

The problem involves calculating the height of a cliff based on the time it takes for a rock to fall and the sound of the splash to return. The total time given is 3.4 seconds, which includes both the fall time and the sound travel time. The correct approach requires setting up two equations: one for the distance the rock falls and another for the distance the sound travels. The height of the cliff is approximately 56 meters, but the fall time is less than 3.4 seconds, necessitating a system of equations to solve accurately.

PREREQUISITES
  • Understanding of kinematic equations, specifically r = ut + 1/2at²
  • Knowledge of sound speed, specifically 340 m/s
  • Ability to set up and solve systems of equations
  • Familiarity with basic physics concepts of motion and sound
NEXT STEPS
  • Learn how to derive equations for free fall motion under gravity
  • Study the relationship between time, distance, and speed in sound propagation
  • Explore systems of equations and methods for solving them
  • Investigate the effects of air resistance on falling objects
USEFUL FOR

Students studying physics, particularly those focusing on kinematics and sound, as well as educators looking for practical examples of motion and sound interaction.

PhysGoat
Messages
2
Reaction score
0

Homework Statement


A person throws a rock off a cliff and hears the splash below 3.4 seconds later. If we know the speed of sound is equal to 340m/s how high is the cliff to the nearest metre?


Homework Equations


I've been trying to use, r = ut + 1/2at2 and
v2 = u2 +2ar and
v= u + at


The Attempt at a Solution


I know that the height of the cliff should be around 56 m as:

r = 0 + 4.9(3.4)2

But i don't know how to factor in the time delay of the sound :(

The answer is: (Spoiler)
52 m

Thanks
 
Physics news on Phys.org
PhysGoat said:
I know that the height of the cliff should be around 56 m as:

r = 0 + 4.9(3.4)2

But i don't know how to factor in the time delay of the sound :(

Welcome to PF!

Hint: it does not take 3.4 seconds for the rock to fall, it takes slightly less than that.
 
Nice problem, i like it. You should set up a system of 2 equations. One will be the distance when the rock falls down and the other the distance when the sound comes up.
What is the relation between the two equations and what is the relation between the two times?
 

Similar threads

  • · Replies 1 ·
Replies
1
Views
1K
  • · Replies 2 ·
Replies
2
Views
6K
Replies
8
Views
7K
  • · Replies 9 ·
Replies
9
Views
3K
  • · Replies 3 ·
Replies
3
Views
13K
  • · Replies 6 ·
Replies
6
Views
5K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 1 ·
Replies
1
Views
5K
Replies
3
Views
12K
Replies
3
Views
2K