What is the kinetic energy of a falling rock?

Click For Summary

Discussion Overview

The discussion revolves around calculating the kinetic energy of a stone dropped from a height of 100 meters, including determining its final velocity upon impact. The scope includes homework-related problem-solving and application of physics concepts such as conservation of energy and kinetic energy formulas.

Discussion Character

  • Homework-related
  • Mathematical reasoning

Main Points Raised

  • One participant presents a formula for final velocity, v = √(2gx), and calculates a value of 31.3 m/s, questioning its correctness.
  • Another participant asks if the first is familiar with the conservation of energy or the kinetic energy formula, implying these concepts are relevant for the calculation.
  • A later post reiterates the final velocity calculation, suggesting a revised value of 44.27 m/s, while also expressing uncertainty about calculating kinetic energy.
  • One participant indicates that mass is not needed for the final velocity calculation but is necessary for determining kinetic energy.
  • Another participant suggests reading a Wikipedia page about kinetic energy for further understanding.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the correct final velocity, with differing calculations presented. There is also uncertainty regarding the calculation of kinetic energy, indicating that the discussion remains unresolved.

Contextual Notes

There are limitations in the discussion, including potential misunderstandings about the application of mass in the velocity calculation and the kinetic energy formula. The assumptions regarding the conditions of the fall and the definitions of terms are not fully explored.

The Futur
Messages
17
Reaction score
0

Homework Statement


b) A person standing on the edge of a 100 m high cliff drops a 0.5 kg stone vertically downwards. Determine the final velocity of the stone after falling 100m, and its kinetic energy.


Homework Equations


Final velocity
v = √(2gx)

The Attempt at a Solution



final velocity

v = √(2gx)
v = √(2(0.5x9.8)100)
v= 31.3m/s
is that correct?

how do i calculate the kinetic energy?
 
Physics news on Phys.org
The Futur said:
how do i calculate the kinetic energy?

Are you familiar with conservation of energy or the kinetic energy formula?
 
Last edited:
The Futur said:

Homework Statement


b) A person standing on the edge of a 100 m high cliff drops a 0.5 kg stone vertically downwards. Determine the final velocity of the stone after falling 100m, and its kinetic energy.


Homework Equations


Final velocity
v = √(2gx)

The Attempt at a Solution



final velocity

v = √(2gx)
v = √(2(0.5x9.8)100)
v= 31.3m/s
is that correct?

how do i calculate the kinetic energy?

The velocity is wrong. You don't use the mass to calculate it (see your formula).
The mass is used to calculate the kinetic energy.
 
so it will be

v = √(2gx)
v = √(2(9.8)100)
v= 44.27m/s ?

and no i don't know how to calculate the second part
 
The Futur said:
so it will be

v = √(2gx)
v = √(2(9.8)100)
v= 44.27m/s ?

and no i don't know how to calculate the second part

Read the page of Wikepedia about kinetic energy
http://en.wikipedia.org/wiki/Kinetic_energy
 

Similar threads

  • · Replies 1 ·
Replies
1
Views
2K
Replies
6
Views
1K
Replies
6
Views
2K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 1 ·
Replies
1
Views
2K
Replies
1
Views
2K
Replies
1
Views
1K
  • · Replies 20 ·
Replies
20
Views
3K
Replies
23
Views
3K
  • · Replies 15 ·
Replies
15
Views
3K