Physics: Post your doubts here!

[princess Anu]

When you stretch a spring, we do work. If we then release the spring, some of the energy is recovered. Some is lost. When they say " net " work done, they're talking about the total work done.

The arrows going up signify that the spring is being loaded, and thus we call it the loading phase. The arrow that's going down is when the spring is released, it's now compressing. This is called the unloading phase. The area which is X and Y, is commonly known as " Hysteresis ".

Hysteresis is basically the energy lost during the stretching and releasing. This leaves us with Z, which is said to be the net work done.

My advice to you would be to think that whatever is outside that area of hysteresis, is the net work done. Hope that helps ^_^

But what I thought was; they are saying NET work done ON the sample .. doesn't that mean work done by stretching a spring (or work done by us). Had they asked Net Work Done BY THE SAMPLE, Z should have been the answer?

 

[Xylferion]

But what I thought was; they are saying NET work done ON the sample .. doesn't that mean work done by stretching a spring (or work done by us). Had they asked Net Work Done BY THE SAMPLE, Z should have been the answer?

I think a hint lies within the word " net ". From what I know, net and resultant are one of the same. For example, when 3 N acts to the left and 4 N to the right, they say the net force/resultant force acting is 1 N to the right... Which leads me to believe that when they say net work done, they're referring to work done despite the energy lost due to hysteresis..

Also work done by the sample is completely irrelevant because it cannot stretch nor compress itself without some external force being applied.

I think the best way to think of it is the resultant amount of elastic strain energy after recovery. ( Work done and elastic strain energy are also one of the same )

 

[ZaqZainab]

any one here has notes for section B physic paper4 I am having really hard time ans I find it really confusing please help

 

[princess Anu]

help

 

[Medallion]

Hi, does anyone know how to solve this? How do you know which forces are going to the clockwise and the anti clockwise direction?? Please help Thank you!!!

 

[Sarosh Jameel]

SOMEONE !!!

 

[Sarosh Jameel]

Hi, does anyone know how to solve this? How do you know which forces are going to the clockwise and the anti clockwise direction?? Please help Thank you!!!View attachment 51679

Clockwise moment = 300 * 0.8* = 240 Nm

Anticlockwise moment = 200*0.8 = 160 Nm

We need more anticlockwise moment to attain equilibrium..
THUS >> 240-160= 80 Nm

80 Nm anticlockwise will bring equilibrium to the system ...
THUS D !!

 

[princess Anu]

help!

 

[princess Anu]

Hi, does anyone know how to solve this? How do you know which forces are going to the clockwise and the anti clockwise direction?? Please help Thank you!!!View attachment 51679

What is the answer?

 

[manya]

can someone help me with this question

 

[Itsmeeee]

Can Someone Please Help Me?

 

[manya]

check q 41 at
http://physics-ref.blogspot.com/2014/11/physics-9702-doubts-help-page-7.html

thankyou so much but i dont understand becuse x is moving up and y is moving down. what would be the phase difference if the wave was like this

 

[The Sarcastic Retard]

Hi, does anyone know how to solve this? How do you know which forces are going to the clockwise and the anti clockwise direction?? Please help Thank you!!!View attachment 51679

Sum of clockwise moments = sum of anticlockwise moments.
0.4*300 = 0.8*200
120 = 160
Hence total torque produced will be 160 - 120 = 40 Anticlockwise = B

 

[The Sarcastic Retard]

help!

for q11 : Is answer D?
For q8 : Is it B?
For Q14 : C?

 

[The Sarcastic Retard]

Can Someone Please Help Me?

Increase in force = resultant force of y - of x
2[120cos(55)] – 2[100(cos(65)] = 53N

 

[manya]

it would still be zero. remember it's a stationary wave

oh okay thankyou so much

 

[manya]

thankyou so much but i dont understand becuse x is moving up and y is moving down. what would be the phase difference if the wave was like this

also can u help me with same question part c4 i understand the explanation u hv given but incase it was 0.5t will we draw the wave like this

 

[Physux]

Need help.

 

[princess Anu]

for q11 : Is answer D?
For q8 : Is it B?
For Q14 : C?

Q8 is A and Q11 is B while Q14 is C
Can u show how you solved Q14

 

[Itsmeeee]

Increase in force = resultant force of y - of x
2[120cos(55)] – 2[100(cos(65)] = 53N

Thank you soo much