Conservation of Work and Energy

In summary, the conversation discusses how to deduce the equation for "Just after impact" in a problem involving motion under constant acceleration. The formula is derived using the same logic as the formula for "Just before impact" and by considering the conservation of energy in the system after the collision. The assumption that the initial velocity is 0 is based on the previous diagram.
  • #1
CivilSigma
227
58

Homework Statement


Hello, I am having trouble understanding the logic behind the solution to the posted problem. How did they deduce the equation for "Just after impact" ? I don't see how
$$v_y = \sqrt{2g(0.6)}$$

What assumptions did they make or how did they get this simplified equation?

I understand how they got the formula for "Just before impact"

In the y direction:
$$mg(1.6)+0.5m(0)^2 = mg(0)+0.5mv_f^2$$
$$v = \sqrt{2g(1.6)}$$

But I don't see how they applied this formula for "just after impact"

Any guidance is really appreciated.

Thank you for your time.

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  • #2
They are applying the formula for motion under constant acceleration because there is a resultant force acting on the plate. It is actually v2=u2+2as
 
  • #3
So what happened to u2 ? Why is it assumed to be 0 here?
 
  • #4
sakonpure6 said:

Homework Statement


Hello, I am having trouble understanding the logic behind the solution to the posted problem. How did they deduce the equation for "Just after impact" ? I don't see how
$$v_y = \sqrt{2g(0.6)}$$I understand how they got the formula for "Just before impact"

In the y direction:
$$mg(1.6)+0.5m(0)^2 = mg(0)+0.5mv_f^2$$
$$v = \sqrt{2g(1.6)}$$

Apply the same logic for the energy of the system after collision.
 
  • #5
u is not assumed to be 0. Look back at the previous diagram and u will know why =)
 
  • #6
sakonpure6 said:
I understand how they got the formula for "Just before impact"

In the y direction:
$$mg(1.6)+0.5m(0)^2 = mg(0)+0.5mv_f^2$$
$$v = \sqrt{2g(1.6)}$$

But I don't see how they applied this formula for "just after impact"
Use the same equation for conservation of energy mgh+0.5mvy2=constant, but with initial height 0 and velocity unknown and final velocity zero at height 0.6 m.
 

1. What is conservation of work and energy?

The conservation of work and energy is a fundamental law of physics that states that the total amount of energy in a closed system remains constant. This means that energy can neither be created nor destroyed, but can only be transformed from one form to another.

2. How does conservation of work and energy apply to real-life situations?

Conservation of work and energy applies to almost all real-life situations involving energy. For example, when a car is in motion, its kinetic energy is converted into heat energy due to friction. However, the total amount of energy remains constant.

3. What are the different forms of energy that are conserved?

The different forms of energy that are conserved include kinetic energy (energy of motion), potential energy (energy stored in an object's position or state), thermal energy (energy due to temperature difference), chemical energy (energy stored in chemical bonds), nuclear energy (energy stored in the nucleus of an atom), and electromagnetic energy (energy of light and other electromagnetic waves).

4. Can energy be transferred from one form to another?

Yes, energy can be transferred from one form to another. This is known as energy conversion. For example, a light bulb converts electrical energy into light energy, and a car engine converts chemical energy into kinetic energy.

5. How is the principle of conservation of work and energy related to the concept of entropy?

The principle of conservation of work and energy is closely related to the concept of entropy, which is a measure of the disorder or randomness in a system. According to the second law of thermodynamics, the total entropy of a closed system always increases over time. This means that energy is constantly being transformed into less usable forms, such as heat, and cannot be completely converted back into its original form.

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