Simple Energy Problem Im missing something

  • Thread starter Thread starter Stevedye56
  • Start date Start date
  • Tags Tags
    Energy
Click For Summary
The discussion centers on calculating the force exerted by the ground on a 20.0 kg coyote that falls 30.0 m and creates a dent of 0.420 m upon impact. The initial potential energy is calculated as 6,000 J, which is converted into kinetic energy just before hitting the ground. Participants clarify that the force exerted by the ground is not simply the weight of the coyote (mg) but involves the work done during the impact. The key point is to consider both gravitational force and the opposing force from the ground to determine the net force during the collision. Understanding this interaction is crucial for accurately calculating the force involved.
Stevedye56
Messages
402
Reaction score
0
The coyote, whose mass is 20.0kg, is chasing the roadrunner when the coyote accidentally runs off the edge of a cliff and plummets to the ground 30.0m below. What force does the ground exert on the coyote as he makes a coyote-shaped dent .420m deep in the ground?

I know that he hits the ground with a force of 6,000J becasue the PE=mgh at the top, Assuming that none of his energy is lost to air resistance he will hit the ground with that same force because all of the potential energy will be converted into kinetic energy. I am just not sure how to get the force. I know F=ma but that seems just to simple.


Any help at all will be appreciated.

Thanks for looking,

Steve
 
Physics news on Phys.org
Stevedye56 said:
What force does the ground exert on the coyote as he makes a coyote-shaped dent .420m deep in the ground?

Do you mean, what is the force which the ground exerts on the coyote while he's been slammed into the ground? If so, use the fact that the change of kinetic energy from the position above the ground to the position when the coyote is stuck in the ground (where his speed = 0) equals the sum of work of gravity (i.e. the coyote's weight) and the work of the force which the ground exerts on him, along the displacement of 0.42 [m]. I hope I didn't miss something.
 
radou said:
Do you mean, what is the force which the ground exerts on the coyote while he's been slammed into the ground? If so, use the fact that the change of kinetic energy from the position above the ground to the position when the coyote is stuck in the ground (where his speed = 0) equals the sum of work of gravity (i.e. the coyote's weight) and the work of the force which the ground exerts on him, along the displacement of 0.42 [m]. I hope I didn't miss something.


Im not sure i understand what your are saying. Are you saying that the force is just mg? Or am i not reading correctly
 
Stevedye56 said:
Im not sure i understand what your are saying. Are you saying that the force is just mg? Or am i not reading correctly

No, the force is not just mg. While being slammed into the ground, the forces acting on the coyote are gravity, and the force which the ground exerts on the coyote (in the opposite direction than gravity), which is the force you need to find.
 
The book claims the answer is that all the magnitudes are the same because "the gravitational force on the penguin is the same". I'm having trouble understanding this. I thought the buoyant force was equal to the weight of the fluid displaced. Weight depends on mass which depends on density. Therefore, due to the differing densities the buoyant force will be different in each case? Is this incorrect?

Similar threads

  • · Replies 5 ·
Replies
5
Views
4K
  • · Replies 1 ·
Replies
1
Views
4K
  • · Replies 2 ·
Replies
2
Views
3K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 3 ·
Replies
3
Views
5K
  • · Replies 3 ·
Replies
3
Views
5K
Replies
6
Views
2K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 16 ·
Replies
16
Views
6K
  • · Replies 7 ·
Replies
7
Views
4K