Physics: Post your doubts here!

[Rohaan Nadeem]

In simple harmonic motion, one of the formulas of Time period of a pendulum is (T=2 pi underoot l/g)
If a lift is moving with upward acceleration, a, then a pendulum inside it will have g=9.81+a because of the total value of g, acceleration of 9.81 m/s sq. was used to cancel acceleration due to gravity so it will also be added into a.
But if a lift is moving with downward acceleration, a, why will the value of g be 9.81-a?

The force that makes the pendulum swing is centripetal, therefore any force acting or acceleration produced is directed towards the centre of circle ( in this case, it's imaginary and the pendulum is the radius).
Hence, acceleration would be in the direction against gravity and total gravity would equal to 9.81-a (downward-upward).

 

[Charlotte20102013]

3 and 11 are answered as solution 151 and 162 at
http://physics-ref.blogspot.com/2014/11/physics-9702-doubts-help-page-26.html
http://physics-ref.blogspot.com/2014/11/physics-9702-doubts-help-page-27.html

respectively

For Q3 Is the life span of a man really 2x10^9 s??? WHy isn't the answer D?

 

[marduk]

june 13 paper 11 question number 19. can help me with it?

 

[Paris Palmer]

In simple harmonic motion, one of the formulas of Time period of a pendulum is (T=2 pi underoot l/g)
If a lift is moving with upward acceleration, a, then a pendulum inside it will have g=9.81+a because of the total value of g, acceleration of 9.81 m/s sq. was used to cancel acceleration due to gravity so it will also be added into a.
But if a lift is moving with downward acceleration, a, why will the value of g be 9.81-a?

Thankyou

 

[Paris Palmer]

The force that makes the pendulum swing is centripetal, therefore any force acting or acceleration produced is directed towards the centre of circle ( in this case, it's imaginary and the pendulum is the radius).
Hence, acceleration would be in the direction against gravity and total gravity would equal to 9.81-a (downward-upward).

Thankyou

 

[PlutoHuman]

papers.xtremepapers.com/CIE/Cambridge%20International%20A%20and%20AS%20Level/Physics%20(9702)/9702_w10_qp_11.pdf
please help with question 9

 

[Thought blocker]

papers.xtremepapers.com/CIE/Cambridge%20International%20A%20and%20AS%20Level/Physics%20(9702)/9702_w10_qp_11.pdf
please help with question 9

Here

 

[Charlotte20102013]

just convert it into years and see what ans you obtain

Right... Silly me.. Hahah! Thanks again!

 

[princess Anu]

this?

 

[Rohaan Nadeem]

Power = Work/ time......(1)
Work = Force*distance.....(2)

(1) => power = Force*speed
power= (1000+10000) *.5 = 5.5 kW

You need to add the 1000 N force required to overcome resistive forces.

 

[princess Anu]

this too ,please!

 

[princess Anu]

 

[princess Anu]

 

[princess Anu]

 

[princess Anu]

Q11,12 ,13 please. Classified Topic 6 page 74

 

[princess Anu]

can u solve MCQ 8 and 15 0f the same topic pleasee

 

[Sewz44]

At the exam do we get a formula sheet for AS physics?
I don't know that that's why I asked.

 

[Sewz44]

Thanx for da help

 

[Enferno]

At the exam do we get a formula sheet for AS physics?
I don't know that that's why I asked.

You get a formula sheet, but it doesnt have all formulas. You can check it, its is on the second and third page of each past paper

 

[Enferno]

For Q3 Is the life span of a man really 2x10^9 s??? WHy isn't the answer D?

2x10^9 is 63.3 years
the real average life span of a man is 68.2 years which is 2.15x10^9. Hence it is incorrect by a factor of LESS THAN 100 not MORE THAN 100