Energy Required To Knock Something Over

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In summary, to figure out the force needed to knock over a can, one can use conservation of energy and find the change in gravitational potential energy between the can's stable position and the position where it is about to tip. This can be calculated by multiplying the mass of the can by 9.8 (gravity) and the height of the can's center of mass. This will give the total force needed to tip the can.
  • #1
sjd0004
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Homework Statement



I need to figure out how much force it would take to knock a can over.

Homework Equations



As of now, I have no clue where to even start with this.

The Attempt at a Solution



I was told by a friend that the way to solve it is by finding the difference between the value at equilibrium and the value when the can is just about to tip. Unfortunately, I have no idea how to do this.
 
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  • #2
sjd0004 said:

Homework Statement



I need to figure out how much force it would take to knock a can over.

Homework Equations



As of now, I have no clue where to even start with this.

The Attempt at a Solution



I was told by a friend that the way to solve it is by finding the difference between the value at equilibrium and the value when the can is just about to tip. Unfortunately, I have no idea how to do this.

Draw a diagram showing a can standing in a stable position. Locate its center of gravity. Now draw the can in a position where it's tipped so it's just balanced and could go either way...fall over or return to its stable position. Where's the center of gravity in that case?
 
  • #3
Okay, I have the diagram drawn. Would I just do the distance between the two points x the force required to get it there? I believe that the formula for work which is equal to energy would be distance * force?
 
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  • #4
sjd0004 said:
Okay, I have the diagram drawn. Would I just do the distance between the two points x the force required to get it there? I believe that the formula for work which is equal to energy would be distance * force?

You could do that, but it could involve a fair amount of effort to sort out the math (the force will be changing direction over the distance it's applied). It would be much simpler to apply conservation of energy. In particular, find the change in gravitational potential energy between the two positions of the center of mass.
 
  • #5
Once the gravitational potential energy difference is found, would the difference of them be the total needed to tip the can?
 
  • #6
sjd0004 said:
Once the gravitational potential energy difference is found, would the difference of them be the total needed to tip the can?

Yes.
 
  • #7
Thank you. One more question though to make sure I have it down. I know that the gpe would be mass*gravity*height. So for the cans would I use the mass of the can*9.8*center of gravity height?
 
  • #8
sjd0004 said:
Thank you. One more question though to make sure I have it down. I know that the gpe would be mass*gravity*height. So for the cans would I use the mass of the can*9.8*center of gravity height?

Right. You use the height of the center of mass of the object to determine the overall GPE for it. While some parts of the object are higher and some are lower (and thus individually have higher or lower GPE's), the sum of the GPE over the whole object will be the same as though all the mass happened to be located at the center of mass.
 

1. What is the definition of energy required to knock something over?

The energy required to knock something over refers to the amount of force needed to cause an object to fall or topple over. It is a combination of the object's weight, its center of mass, and the external force applied to it.

2. How is the energy required to knock something over calculated?

The amount of energy required to knock something over can be calculated using the formula E = mgh, where E is energy, m is the mass of the object, g is the acceleration due to gravity, and h is the height at which the object is being knocked over from.

3. Does the energy required to knock something over depend on the shape of the object?

Yes, the shape of an object can affect the energy required to knock it over. Objects with a wider base, such as a pyramid, require less energy to topple over compared to objects with a narrow base, such as a pencil.

4. Can the energy required to knock something over be increased or decreased?

Yes, the energy required to knock something over can be increased or decreased by changing the height or angle at which the object is being knocked over from. It can also be affected by the surface on which the object is placed and the force applied to it.

5. How does friction play a role in the energy required to knock something over?

Friction can increase the energy required to knock something over as it creates resistance between the object and the surface it is on. This can make it harder to topple over the object and more force would be needed to overcome the friction and knock it over.

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