Trouble with Conservation of Energy And Friction

In summary, the conversation is about trying to account for the initial and final energy of a hockey puck moving across ice. The formula for initial energy is .5mv02 and the formula for heat released is Eth=μknΔx. To find Δx, the time it takes for the puck to come to rest is calculated using the formula .5at2+v0t=Δx. There is confusion about why the mass (m) is not accounted for when setting Ei equal to Eth.
  • #1
MrBillyShears
Gold Member
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Ok, I'm driving myself mad, so if someone could settle this for me, that would be helpful. So, I'm imagining something like a hockey puck going across ice and coming to a stop. I'm trying to account for the initial energy, Ei, and the final energy, Ef. So this hockey puck starts with a velocity, v0, a mass, m, and of course under the influence of gravity, g. So, its Ei is.5mv02. Now, to account for the heat released, you use Eth=μk∫ndx, (n is the normal force). Now, since n is constant in this case, it reduces to Eth=μknΔx. Now we find Δx by finding the time it takes for the puck to come to rest, at+v0=0, -μkgt+v0=0, then we put that time in for the formula, .5at2+v0t=Δx. Then, we set Ei equal to Eth, but I get .5mv02=.5v02, so, what happened to the m? Why am I not getting equal things?
 
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  • #2
Never mind, my mistake. Don't know how to delete it.
 

Related to Trouble with Conservation of Energy And Friction

1. What is the Law of Conservation of Energy?

The Law of Conservation of Energy states that energy cannot be created or destroyed, it can only be converted from one form to another. This means that the total amount of energy in a closed system remains constant over time.

2. How does friction affect the conservation of energy?

Friction is a force that opposes motion and converts kinetic energy into heat. This means that a portion of the energy in a system is lost due to friction, so the total energy is not conserved. However, this energy is not destroyed, it is just converted into a different form.

3. Can conservation of energy be violated?

No, the Law of Conservation of Energy is a fundamental principle in physics and has been confirmed by numerous experiments. Any apparent violations of this law can be explained by the conversion of energy into different forms or the presence of external forces.

4. How can friction be reduced to improve conservation of energy?

Friction can be reduced by using lubricants, smooth surfaces, or designing objects with streamlined shapes. Reducing friction can help to minimize the loss of energy in a system and improve its overall efficiency.

5. What are some real-world examples of the conservation of energy and friction?

One example is a pendulum. As it swings back and forth, the potential energy at the top of the swing is converted into kinetic energy as it moves down. However, friction from air resistance and friction at the pivot point will cause the pendulum to eventually come to a stop. Another example is a car using brakes to slow down. The kinetic energy of the car is converted into heat due to friction between the brake pads and the wheels, ultimately reducing the car's speed.

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