Physics: Post your doubts here!

[Shimmery woods]

que 37 please.. im getting 0.75 which is not even in the options

 

[Mstudent]

help me with que 15 please

You must realise that this is a uniform block so the centre of mass is right in the center

Hope this helps

 

[Holmes]

You must realise that this is a uniform block so the centre of mass is right in the center

Hope this helps

good shot boy

 

[Mstudent]

good shot boy

Thanks mate!

 

[Holmes]

Can any one EXPLAIN me Q's 16 ,34, 38. Paper link is given below.
http://papers.gceguide.com/A Levels/Physics (9702)/9702_w13_qp_13.pdf
Thanks in Advance.

 

[Mstudent]

q.16

Its to do with the random motion of the atoms and molecules of a substance

Internal energy is defined as the energy associated with the random, disordered motion of molecules.

http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/inteng.html

 

[Holmes]

q.16

Its to do with the random motion of the atoms and molecules of a substance

Internal energy is defined as the energy associated with the random, disordered motion of molecules.

http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/inteng.html

sorry the link is
http://papers.gceguide.com/A Levels/Physics (9702)/9702_w13_qp_13.pdf

 

[Mstudent]

sorry the link is
http://papers.gceguide.com/A Levels/Physics (9702)/9702_w13_qp_13.pdf

For q.16

You have a train which is moving. It has a resultant force from the engines due to the total resistive force
The resistive force is divided into two types, air resistance and wheel friction. They want to know they ratio of air resistance to wheel friction of the total resistive force at a given time

Hope that helps

 

[amina1300]

Can any one EXPLAIN me Q's 16 ,34, 38. Paper link is given below.
http://papers.gceguide.com/A Levels/Physics (9702)/9702_w13_qp_13.pdf
Thanks in Advance.

Q34
P = I^2 R 4.0=I^2(20)
Current in circuit = 0.45 A
V=Ir = 0.45*20 = 9.0 V
From kirchhoff's 2 law 16= 9+0.45R R= 16

Q38

 

[amina1300]

que 30 ...i could get to the part mgd/V but why do we multpily it with e ?
F = E×q
m×g = E ×q
m×g = V÷d × q
mgd/V = q ...how do i get the value of n ?

You did everything right. you just replace q with n*e

 

[amina1300]

http://papers.gceguide.com/A Levels/Physics (9702)/9702_w16_qp_12.pdf
Q10 20 22 24 26 29 31 37 39 ??

 

[amina1300]

Q10 20 22 24 26 29 31 37 39 ?? PLEASE EXPLAIN!!

http://papers.gceguide.com/A Levels/Physics (9702)/9702_w16_qp_12.pdf

 

[Mstudent]

F

Q10 20 22 24 26 29 31 37 39 ?? PLEASE EXPLAIN!!

http://papers.gceguide.com/A Levels/Physics (9702)/9702_w16_qp_12.pdf

or q.22

The 10kn load is shared by 4 rods , so just divide the 10*10^3 by four and solve to find the young's modulus!

 

[Mstudent]

Q10 20 22 24 26 29 31 37 39 ?? PLEASE EXPLAIN!!

http://papers.gceguide.com/A Levels/Physics (9702)/9702_w16_qp_12.pdf

Y1 will occur again 1/4 lamda later and 1 lamda later

 

[Mstudent]

Q10 20 22 24 26 29 31 37 39 ?? PLEASE EXPLAIN!!

http://papers.gceguide.com/A Levels/Physics (9702)/9702_w16_qp_12.pdf

q.29
the distance between two adjacent antinodes(maxima) in a stationary wave is 1/2 lamda, so 1 lambda is 1.5cm * 2= 3cm= 0.03m

f=v/lamda (wave equation)

v= 3.00*10^8 (given in first pg of exam paper) (microwave is light)

3.00*10^8 / 0.03 = 1*10^10 which is C

 

[Mstudent]

Q10 20 22 24 26 29 31 37 39 ?? PLEASE EXPLAIN!!

http://papers.gceguide.com/A Levels/Physics (9702)/9702_w16_qp_12.pdf

q.39

in beta- decay neutron breaks into proton and neutron, so the unstable neuclide before decaying had the same nucleon number(nucleon number doesn't change in beta decay) and 1 less proton.

 

[furuta]

someone please explain me these two questions:

• A sprinter runs a 100 m race in a straight line. He accelerates from the starting block at a constant acceleration of 2.5 m s–2 to reach his maximum speed of 10 m s–1. He maintains this speed until he crosses the finish line. Which time does it take the sprinter to run the race? A 4s B 10s C 12s D 20s. Answer is C, how?
• An insect jumps with an initial vertical velocity of 1.0ms–1, reaching a maximum height of 3.5 × 10–2 m. Assume the deceleration is uniform. What is the magnitude of the deceleration? A 3.6ms–2 B 9.8ms–2 C 14ms–2 D 29ms–2 . Answer is C, how?

Thank you c:

 

[Mstudent]

someone please explain me these two questions:

• A sprinter runs a 100 m race in a straight line. He accelerates from the starting block at a constant acceleration of 2.5 m s–2 to reach his maximum speed of 10 m s–1. He maintains this speed until he crosses the finish line. Which time does it take the sprinter to run the race? A 4s B 10s C 12s D 20s. Answer is C, how?
• An insect jumps with an initial vertical velocity of 1.0ms–1, reaching a maximum height of 3.5 × 10–2 m. Assume the deceleration is uniform. What is the magnitude of the deceleration? A 3.6ms–2 B 9.8ms–2 C 14ms–2 D 29ms–2 . Answer is C, how?

Thank you c:

For second q. use v^2=u^2 + 2as

 

[furuta]

For second q. use v^2=u^2 + 2as

yes, thank you, I used that but im still not getting the answer..?

 

[Mstudent]

yes, thank you, I used that but im still not getting the answer..?

(v^2)-(u^2)=(0)-(1.0^2)= -1.0
2s = 2*3.5*10^-2=0.07
a=1.0/0.07 = -14.2857ms^-2