Physics: Post your doubts here!

[Dream.Eater]

How to add up spring constants?
(springs in series and parallel)

Exactly what i was searching for XD

 

[Dream.Eater]

Why is the answer C ?

 

[Dr Death]

View attachment 51312 Why is the answer C ?

According to energy conservation law, total energy can never be changed. Energy can never be destroyed.

When the object strikes anything. If it is an inelastic collision, the kinetic energy is given off at collision as sound energy or thermal energy or some other form of energy ( see.. energy is given off.. not destroyed).

Therefore KE lost is dissipated and is not conserved.

Now you may ask : How is possible given that the formula of momentum is mv and the formula of kinetic energy is 0.5mv^2; both are dependent on mass and velocity.

Let's take an example with simple numbers :

1+2=3

3+0=3

This can represent the momentum conservation. Now look at the sum of squares :

1*1+2*2=5

3*3+0*0=9

The sum is not conserved because the momentum that was transferred changed differently the result of the squares. In a word, kinetic energy doesn't change linearly with speed (which is obvious since it's a square).

Hope this helped

 

[Dream.Eater]

Can someone please explain this?

 

[Dream.Eater]

According to energy conservation law, total energy can never be changed. Energy can never be destroyed.

When the object strikes anything. If it is an inelastic collision, the kinetic energy is given off at collision as sound energy or thermal energy or some other form of energy ( see.. energy is given off.. not destroyed).

Therefore KE lost is dissipated and is not conserved.

Now you may ask : How is possible given that the formula of momentum is mv and the formula of kinetic energy is 0.5mv^2; both are dependent on mass and velocity.

Let's take an example with simple numbers :

1+2=3

3+0=3

This can represent the momentum conservation. Now look at the sum of squares :

1*1+2*2=5

3*3+0*0=9

The sum is not conserved because the momentum that was transferred changed differently the result of the squares. In a word, kinetic energy doesn't change linearly with speed (which is obvious since it's a square).

Hope this helped

What i really needed to know was why momentum is conserved but thanks anyway for this and all the other questions you helped me out with today!

 

[Dr Death]

What i really needed to know was why momentum is conserved but thanks anyway for this and all the other questions you helped me out with today!

THX to u too. Also I found the spring constant thing from a friend

 

[princess Anu]

Nope.
If that's a velocity time graph then yeah.. But displacement should increase rapidly at first, then comparatively slowly. Should not decrease

why? displacement can decrease.. its distance that cannot

 

[Dr Death]

why? displacement can decrease.. its distance that cannot

Yes. Displacement can decrease. But it shouldn't in your case.
Tell me where the displacement is taken from

 

[princess Anu]

Yes. Displacement can decrease. But it shouldn't in your case.
Tell me where the displacement is taken from

why ? as the velocity is changing its direction , the gradient has to become -ve no?

 

[Dr Death]

View attachment 51321

Can someone please explain this?

Use equation d sin θ = n λ
λ = 590 nm
n = 2
θ = 43
d is answer.

 

[The Godfather]

How to add up spring constants?
(springs in series and parallel)

How to add up spring constants?
(springs in series and parallel)

If two sprinsgs are in parallel then spring constant = 2k
If three sprinsgs are in parallel then spring constant = 3k
And so on...
If two springs are in series then spring constant = k/2
If three springs are in series then spring constant = k/3
And so on..

 

[Dr Death]

why ? as the velocity is changing its direction , the gradient has to become -ve no?

Velocity is not changing direction. If it is, then the ball should NOT be traveling with constant velocity. It should be decelerating.

If you are taking the displacement from the start position, and the ball is continuously rolling, the displacement should only increase. NOT decrease.
If I have misunderstood your question and the ball is going to come back up the slope THEN your answer is correct

 

[The Godfather]

What i really needed to know was why momentum is conserved but thanks anyway for this and all the other questions you helped me out with today!

The momentum of the system is always conserved wehther it is elastic collision or inelastic collision.

 

[RAMEEZA]

can anybody plzzzzz tell about what is mechanical work and mechanical energy

 

[The Godfather]

can anybody plzzzzz tell about what is mechanical work and mechanical energy

http://lightandmatter.com/html_books/lm/ch13/ch13.html

 

[Mahnoorfatima]

I don't get why is the force P acting specifically in this angle. Why can't the answer be A? Can someone explain it diagrammaticaly please? http://papers.xtremepapers.com/CIE/...nd AS Level/Physics (9702)/9702_s12_qp_12.pdf

 

[Dr Death]

I don't get why is the force P acting specifically in this angle. Why can't the answer be A? Can someone explain it diagrammaticaly please? http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_s12_qp_12.pdf

4 th question?

 

[Mahnoorfatima]

http://papers.xtremepapers.com/CIE/...nd AS Level/Physics (9702)/9702_s12_qp_12.pdf
And in question 22, why don't we find the denisty of a single atom?

 

[Mahnoorfatima]

4 th question?

14th

 

[Dr Death]

4 th question?

14th

Lemme explain. At instance of release, it begins to slide.
Question mentioned that the wall is rough and ground is frictionless