Conservation of Energy/Angular Momentum

In summary: H in part (a) is the height the block would rise if it just coasted to the top, while H in part (b) is the height the block would rise if it started from the bottom and ramped up.
  • #1
velvetymoogle
24
0

Homework Statement


Hi.
The problem is "A wooden block of mass m slides with an initial speed of vi up a straight incline that makes an angle of theta with the horizontal. If the incline is rough with a coefficient of kinetic friction uk, determine the maximum height it rises in terms of h found in part a (which was H = vi^2/2g)"


Homework Equations


conservation of energy
You can only use m (mass of block), vi (initial velocity), theta, and g (gravity)


The Attempt at a Solution


KE at the bottom = PE at the top + Work.
mgh + Fd = 1/2mv^2
h = [mvi^2 - ukmgcos(theta)d]/mg
Problem is, I don't know what d is and it can't be part of my final answer. I know it's the distance that the block travels up the ramp, but how do I figure that out?
Also, since it says in terms of h found in part a, does that mean I set everything equal to vi^2/2g?

How would I do this with a hoop with radius R?
 
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  • #2
So, you correctly applied the conservation of mechanical energy. :smile:
Could you right d as a function of h and [itex]\theta[/itex]? :rolleyes:

The hoop will have in the end not only linear velocity but also angular velocity. Apply again conservation of mechanical energy, but this time consider also the kinetic rotational energy. :-p
 
  • #3
Okay this is going to sound really confusing but am I on the right path for the block one?

I got to the point where gh = 1/2(vi)^2 - ukg(cot(theta))h
At this point, do I plug in what I got for H in part (a) since it wants it says "in terms of h found in part a"? What exactly are they asking me to do?
 
  • #4
Nevermind. I was being stupid and forgot they are two different H's
 

Related to Conservation of Energy/Angular Momentum

1. What is conservation of energy and angular momentum?

Conservation of energy and angular momentum are fundamental principles in physics that state that these quantities cannot be created or destroyed, but can only be transferred or transformed from one form to another.

2. Why are conservation of energy and angular momentum important?

These principles are important because they help us understand and predict the behavior of objects in motion. They also play a crucial role in many practical applications, such as in the design of machines and structures.

3. How is energy conserved in a closed system?

In a closed system, energy is conserved because the total amount of energy remains constant. This means that any energy that is lost in one form must be gained in another form, ensuring that the total energy remains the same.

4. Can conservation of energy and angular momentum be violated?

No, these principles are considered to be laws of nature and have been extensively tested and proven through experiments. Any apparent violations of these laws can usually be explained by external forces or errors in measurement.

5. How do conservation of energy and angular momentum relate to each other?

Conservation of energy and angular momentum are closely related because they both involve the idea that certain quantities cannot be created or destroyed. In fact, angular momentum can be thought of as a form of energy, and the two principles are often used together to analyze the motion of objects.

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