• We need your support!

    We are currently struggling to cover the operational costs of Xtremepapers, as a result we might have to shut this website down. Please donate if we have helped you and help make a difference in other students' lives!
    Click here to Donate Now (View Announcement)

Physics: Post your doubts here!

Messages
500
Reaction score
419
Points
73
Someone plz tell that what is wrong with statement A

I guess the main focus point here is the Elastic potential energy lost is the area ' X ' for the graph here is force-extension thus, it show lost energy.
But there was another question in june 2013 12 where it asked what the area between the graphs meant and there the correct option was amount of thermal energy dissipated in the rubber.
http://physics-ref.blogspot.com/2018/02/a-rubber-cord-hangs-from-rigid-support.html
I don't know, I am getting confused myself.
 
Messages
884
Reaction score
449
Points
73
I guess the main focus point here is the Elastic potential energy lost is the area ' X ' for the graph here is force-extension thus, it show lost energy.
But there was another question in june 2013 12 where it asked what the area between the graphs meant and there the correct option was amount of thermal energy dissipated in the rubber.
http://physics-ref.blogspot.com/2018/02/a-rubber-cord-hangs-from-rigid-support.html
I don't know, I am getting confused myself.
Maybe then it is the energy 'released as heat' to the surroundings...lol idk:p
 
Messages
300
Reaction score
138
Points
53
Someone plz tell that what is wrong with statement A
This question is really easy and simple. You can easily answer it by understanding that the area under a graph is the work done for a F-x graph. So, the total area under the graph to reach e is the combo of X and Y, thus the answer is B. What I am about to say may confuse you, so you may choose to ignore it. A being incorrect would require a detailed explanation with a diagram(too lazy for that)... but the confusing part about it is that when the spring is going from e to 0, the area under the graph is not Y... it is the area above X(look at it clearly and understand it). So when you shade the area under the graphs for both occasions(1st occasion being 0 to e, 2nd occasion being e to 0). You will end up finding that both of them are equal... hence none of the elastic potential energy is converted to heat energy which tells you that A is wrong.
 
Messages
300
Reaction score
138
Points
53
Bro, if you don't know how to do this, may god bless you for the upcoming exam. Really easy question...
Anyways: firstly, efficiency is the (output/input)*100. In this case, the input is the KE while the output GPE is the input. You find the KE: 1/2*500*2^2. Then all these values in the efficiency formula, the KE as your input, m(9.81)(15) which is your GPE as your output and 10 as your efficiency. You will get the final answer 0.68 kg(B) which is most definitely correct(if it's wrong, I would opt to kill myself).
 
Messages
500
Reaction score
419
Points
73
This question is really easy and simple. You can easily answer it by understanding that the area under a graph is the work done for a F-x graph. So, the total area under the graph to reach e is the combo of X and Y, thus the answer is B. What I am about to say may confuse you, so you may choose to ignore it. A being incorrect would require a detailed explanation with a diagram(too lazy for that)... but the confusing part about it is that when the spring is going from e to 0, the area under the graph is not Y... it is the area above X(look at it clearly and understand it). So when you shade the area under the graphs for both occasions(1st occasion being 0 to e, 2nd occasion being e to 0). You will end up finding that both of them are equal... hence none of the elastic potential energy is converted to heat energy which tells you that A is wrong.

Can you please draw the diagram? I am not getting the idea clearly.
 
Messages
1
Reaction score
0
Points
1

Q. no. 18 Answer:

Kinetic Energy = (1/2)mv^2
= (1/2) x (500) x (2.0)^2
= 1000 J

Since the pump is 10% efficient so,
output energy = 10% of 1000 J
= 100 J
As this energy is used to lift the water, it means that the kinetic energy is converted to potential energy. So,

mgh=100
or m = 100 / (gh)
= 100 / (9.81 x 15)
= 100 / 147.15
= 0.67957866123003737682636765205573
~ 0.68

Therefore, option B is the correct answer.
 
Messages
18
Reaction score
7
Points
13
How do we show if a constant is within the limits of experimental accuracy or not? What method would be best for such questions??
 
Messages
300
Reaction score
138
Points
53
So how do you explain the area bw the two graphs?
You can see both the areas are equal... So the elastic potential energy was same when the spring went from 0 to e and e to 0. So... none of the elastic energy is converted into heat... so A can't be correct since there isn't any energy converted into heat. You can explain this ans more than this.
 
Messages
300
Reaction score
138
Points
53
How do we show if a constant is within the limits of experimental accuracy or not? What method would be best for such questions??
You use a specified criteria like: if the constants have a percentage difference of 20%, they are within limits of experimental accuracy. The criteria you specify is upto you.
 
Messages
18
Reaction score
7
Points
13
You use a specified criteria like: if the constants have a percentage difference of 20%, they are within limits of experimental accuracy. The criteria you specify is upto you.

Okay! So if I get the percentage uncertainty of a measured value as 14% and my constants have %uncertainty of 25% then my value is proportional within the limits right??

I’ve been doing this! Just got confused...
Just out of curiousity, I wanted to know what you do at your side of the globe! Lol!
 
Top