Max KE of a squirrel jumping from the top of a tree

  • Thread starter Thread starter Boop de Boop
  • Start date Start date
  • Tags Tags
    Max Tree
Click For Summary
SUMMARY

The maximum kinetic energy (KE) of a squirrel jumping from a 25 m tall tree with an initial horizontal speed of 8 m/s can be calculated using the conservation of mechanical energy principles. The final velocity upon reaching the ground is determined using the kinematic equation, resulting in a final velocity of 23.74 m/s. The initial kinetic energy is calculated using the formula KE = 0.5mv^2, where the initial velocity is 8 m/s. For the second scenario, where a squirrel jumps 4 m upward, the kinetic energy at various heights can be determined by applying energy conservation principles.

PREREQUISITES
  • Understanding of kinetic energy (KE) and potential energy (PE) formulas: KE = 0.5mv^2, PE = mgh
  • Familiarity with kinematic equations, specifically vf^2 = vi^2 + 2ad
  • Basic knowledge of conservation of mechanical energy principles
  • Ability to differentiate between horizontal and vertical motion in physics
NEXT STEPS
  • Study the application of conservation of energy in projectile motion
  • Learn how to solve problems involving multiple dimensions in physics
  • Explore the differences between kinematics and dynamics in physics
  • Practice calculating kinetic and potential energy in various scenarios
USEFUL FOR

Students studying physics, educators teaching mechanics, and anyone interested in understanding energy conservation in motion scenarios.

Boop de Boop
Messages
5
Reaction score
1

Homework Statement


1. A squirrel jumps horizontally from the top of a 25 m tall tree with a speed of 8 m/s. What is the maximum kinetic energy of the squirrel during it`s entire trip down to the ground from the top of the tree?
2.If another squirrel of the same mass jumps straight upward from the ground well enough to get 4m off the ground and then falls back to the ground, what is the kinetic energy in the following locations and time:
a)3m above ground, on the way up
b)2m above ground, on the way down
c)1m above ground, on the way down

Homework Equations


Pe:mgh
ke:0.5mv^2
pei+kei=pef+kef

The Attempt at a Solution


I know that we have to use the ke initial and add it with the new kinetic energy that is gained during gthe trip in order to calculate total kinetic energy before it hits the ground for prolem 1. But I am really confused and would appreciate guidance. I do not need the answers just help. :)
 
Last edited by a moderator:
Physics news on Phys.org
Boop de Boop said:
I know that we have to use the ke initial and add it with the new kinetic energy that is gained during gthe trip in order to calculate total kinetic energy before it hits the ground for prolem 1
So where are you stuck, finding the initial KE, finding the KE gained in the fall, or in adding the two?
Can't tell what your confusion is without seeing your attempt.
 
I used the kinematic equation vf^2=vi^2+2ad and found final velocity which is 23.74. Then I plugged into ke-)0.5mv^2. I'm confused with kinetic initial. Is it just ke formula but v final is 8
 
Boop de Boop said:
I used the kinematic equation vf^2=vi^2+2ad and found final velocity which is 23.74. Then I plugged into ke-)0.5mv^2. I'm confused with kinetic initial. Is it just ke formula but v final is 8
That kinetic equation is usually used for one dimensional motion, but here the initial velocity and the acceleration are in different directions.
However, it will give the right result here thanks to Pythagoras; see the later Edit below. Suppose we take that equation and multiply it everywhere by ½m:
½mvf2=½mvi2+mad, where d is the height of the descent and a is g. You can see that this represents
Final KE = initial KE + lost GPE.
I.e. it is the equation for conservation of mechanical work.

Edit: if you want to do it by kinetics rather than work conservation, a more usual path would be to treat the horizontal and vertical separately:
vfx2=vix2+0 (no horizontal acceleration)
vfy2=viy2+2(-d)(-g), where viy=0.
Then you can add these to get the square of the landing speed.
 
Last edited:
Boop de Boop said:
A squirrel jumps horizontally from the top of a 25 m tall tree with a speed of 8 m/s. What is the maximum kinetic energy of the squirrel during it`s entire trip down to the ground from the top of the tree?
From energy conservation KEheight+mgh=KEground+0 where KEground is the max. KE
 
Boop de Boop said:
2.If another squirrel of the same mass jumps straight upward from the ground well enough to get 4m off the ground and then falls back to the ground, what is the kinetic energy in the following locations and time:
From energy conservation
KEi+0=KEheight+mgh ,
During upward journey.
During downward journey
mghmax=mgh+KEheight
 
Apashanka said:
From energy conservation KEheight+mgh=KEground+0 where KEground is the max. KE
@Boop de Boop seems to understand that (see post #1), but became confused when trying to solve it with SUVAT equations (see post #3).
By the way @Boop de Boop, you meant "kinetic", not "kinematic". Kinematics concerns the geometry of moving systems. See e.g. https://en.m.wikipedia.org/wiki/Kinematics.
 

Similar threads

Replies
13
Views
24K
Replies
43
Views
5K
  • · Replies 12 ·
Replies
12
Views
12K
  • · Replies 5 ·
Replies
5
Views
8K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 8 ·
Replies
8
Views
4K
  • · Replies 7 ·
Replies
7
Views
2K
  • · Replies 4 ·
Replies
4
Views
2K
Replies
8
Views
3K
  • · Replies 17 ·
Replies
17
Views
4K