The mass of the pendulum bob was determined on an electronic scale and

[alicia113]

The mass of the pendulum bob was determined on an electronic scale and its diamter was measured using calipers. The initial height was measured with a meter stick. At the lowest point of its swing, the pendulum bob broke a photogate light beam. The time interval that the light was interrupted was recorded on an electronic timer attached to the photogate.
Use the following data to complete a report.
MAss of pendulum bob = 240.3 g
Diameter of pendulum bob = 3.50 cm
Initial height of pendulum bob = 48.0 cm
Length of pendulum string = 2.14 m
Time interval of photogate light interruption = 11.8 ms

Your report should include the following:
(a) conclusion as to whether or not the pendulum demonstrated the law of conservation of energy
(b) calculations of the efficiency of the pendulum as a mechanical machine
(c) any statements of sources of error
(d) your suggestions for improving the design of the investigation.
Relevant equations[/b]



3. The Attempt at a Solution

Am I supposed to perform this experiement myself, because they are giving me all the measurments (therefore am I just doing an analysis) I am not quite sure how to go a outs this since they give me everything

To see if it obeys law of conservation Of energy I was going to see if the initial height matches the final hiring using 9.8m/s and my v ... Is that correct and how do I find efficnecy

 

[alicia113]

Oh and I converted grams to kg and cm to m

 

[NoPoke]

the experiment has been carried out for you (imagine that you watched it happening). You are then going to process the results.

I don't know what you mean by "final hiring using 9.8m/s"

What "v" are you referring to? You have yet to give a calculation for v, or to say what v is.

 

[alicia113]

the experiment has been carried out for you (imagine that you watched it happening). You are then going to process the results.

I don't know what you mean by "final hiring using 9.8m/s"

What "v" are you referring to? You have yet to give a calculation for v, or to say what v is.

How do I calculate for v?

 

[alicia113]

I know I use diameter and the 11.8 ms but I don't know the equation

 

[NoPoke]

err you introduced v. I don't know what you mean by v.

By way of an extreme example I'm currently sitting still so my "v" I'd say was currently zero.

 

[alicia113]

err you introduced v. I don't know what you mean by v.

By way of an extreme example I'm currently sitting still so my "v" I'd say was currently zero.

So if I use this equation

1/2mv^2+mgdeltah


It look like this.

0+0.3403 x 9.8m/s^2 x 0.48m?


Which equals 1.6 j as its initial spot at a...

 

[alicia113]

Then for final height I did

0+ mgdeltah= 1.6J
(0.3403)(9.8m/s^2)deltah=1.6J

So delta h = 0.48 therefore it obeys the law?

 

[NoPoke]

the experiment has been carried out for you (imagine that you watched it happening). You are then going to process the results.

I don't know what you mean by "final hiring using 9.8m/s"

What "v" are you referring to? You have yet to give a calculation for v, or to say what v is.

I'm stuck here. I don't know what you mean. I can't help with equations or verifying any answer until I know what steps you plan on using to answer the pendulum problem you have been set.

 

[alicia113]

That's what I used above ?? I don't understand why they gave me so much info

 

[NoPoke]

That's what I used above ?? I don't understand why they gave me so much info

I've covered that...

the experiment has been carried out for you (imagine that you watched it happening). You are then going to process the results.

 

[alicia113]

I've covered that...

And you are saying I need v.. So how to I get that? What equation do I use?

 

[NoPoke]

You said you will use v in your opening post. You did not say what this v that you need is.

You need to say what v is before anyone can help you calculate it.

 

[alicia113]

So v is 0 for the first hieght. The starting hieght at 0.48m r 48cm .. Because it is not moving.


I need to know what v is for the final so I can determine te hieght. So how do I find v when I have calculate the J for E mechancal. As posted above in previouse post

 

[NoPoke]

You still are not saying what v is. For example every pendulum I've ever seen eventually stops so my final value is going to be zero. But that does not help you because I haven't said what I mean by v. On one pendulum clock I saw the escapement broke and the pendulum was thrown across the room. Numbers alone have no meaning.

Describe what you mean by v in words. Make it very clear so there can be no misunderstanding.

 

[alicia113]

Ok v is speed sorry

 

[NoPoke]

speed of what?

 

[alicia113]

Of the pendulum when it hits its final hieght ...

 

[NoPoke]

How will knowing that value help you? [You need a plan for how you are going to answer the question in your opening post]

 

[alicia113]

Yes so my initial speed v is 0m/s as when it starts at intial hieght at 0.48m it is not moving. I need to find out the speed when it moves to the other side and need that hieght I determine if it obeys the law or not.

 

[NoPoke]

well the speed of the pendulum will be zero once it has reached its maximum height on the other side too. What use can you make of this zero? remember it is your answer, and your plan for how to answer that matters.

You don't have a measurement of this second height so it may be a bit tricky to use... However height can be a part of an answer to the question, but maybe not heights that you don't know from the experiment.

 

[NoPoke]

here is a plan that you might like to try..

describe what happens in the experiment. Don't worry about numbers (you can add the ones that are provided later)

Use relevant physics terms, energy, speed, maximum minimum and any others that you think add clarity.

Go through your story seeing at what points you can either state a fact or calculate a value.

Avoid questions in your description. It is a story about what happened during the experiment.

 

[alicia113]

I need the speed that it is falling at though

 

[NoPoke]

I need the speed that it is falling at though

why do you need that?

 

[alicia113]

So I can find its final height

 

[alicia113]

Ok just scratch all of that. New question. How do I find the efficiency ?

 

[PeterO]

The mass of the pendulum bob was determined on an electronic scale and its diamter was measured using calipers. The initial height was measured with a meter stick. At the lowest point of its swing, the pendulum bob broke a photogate light beam. The time interval that the light was interrupted was recorded on an electronic timer attached to the photogate.
Use the following data to complete a report.
MAss of pendulum bob = 240.3 g
Diameter of pendulum bob = 3.50 cm
Initial height of pendulum bob = 48.0 cm
Length of pendulum string = 2.14 m
Time interval of photogate light interruption = 11.8 ms

Your report should include the following:
(a) conclusion as to whether or not the pendulum demonstrated the law of conservation of energy
(b) calculations of the efficiency of the pendulum as a mechanical machine
(c) any statements of sources of error
(d) your suggestions for improving the design of the investigation.
Relevant equations[/b]



3. The Attempt at a Solution

Am I supposed to perform this experiement myself, because they are giving me all the measurments (therefore am I just doing an analysis) I am not quite sure how to go a outs this since they give me everything

To see if it obeys law of conservation Of energy I was going to see if the initial height matches the final hiring using 9.8m/s and my v ... Is that correct and how do I find efficnecy

When the pendulum bob is held in the start position, it has a lot of potential energy and no kinetic energy.
When it swings through its lowest point - where the photogate is - it has lots of kinetic energy and much less Potential Energy.

If the loss in Potential energy equals the gain in kinetic energy, then this pendulum will have demonstrated conservation of energy.
if however, the gain in kinetic energy is only 95% of the potential energy lost, then the pendulum is only 95% efficient.

Your prime objective, to start with, is to calculate the loss of Potential energy and gain in kinetic energy, to see how well the pendulum operates.

 

[NoPoke]

You start with an amount of energy.
You mechanism consumes an amount of energy in operating that does not go towards the desired behaviour. This represents a loss of energy.

The efficiency is calculated from these.
efficiency = (input-loss)/input

You have to decide what the desired behaviour is from your pendulum. You will need to come up with some kind of energy conversion or energy flow statement so you can identify the loss of energy. You don't need to know what is causing the loss only that it has taken place.

====

The initial speed that your pendulum bob falls at is zero, the speed that your pendulum bob falls at as it goes through the light gate is also zero (or so close as to make no difference)

 

[alicia113]

How did you get that ?!?

 

[PeterO]

How did you get that ?!?

Who are you asking?