Physics: Post your doubts here!

[Taci12]

what is not conserved in nuclear processes?

A energy and mass together
B nucleon number
C neutron number
D charge
Why the answer is neutron number? Is the charge is conserved?
someone can help me ??

Neutron number is not conserved as neutrons can decay to form a proton and an electron. Both the initial net charge and final net charge in this nuclear reaction is zero, charge is always conserved.

 

[Taci12]

HI all. Can anyone solve this question for me and explain its concept and working plz. ill be grateful

Question number 4 . part( b ). sub-part (ii).
Paper 4
May/June 2008
Physics

Thanks in advance

Net potential = potential due to A + potential due to B

electric potential = Q/ 4πε0r , here r is given by x

using the first formula:

0= (3.6 × 10–9) / (4πε0 × 18 × 10–2) + q / (4πε0 × 12 × 10–2)
q= –2.4 × 10–9 C

 

[SilverCrest]

Peace be upon you!
Can somebody explain mcq number 10 ,17 and 14 of:
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_s12_qp_13.pdf

And also mcq 17 of:
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_s10_qp_13.pdf
Thank You!

 

[iFuz]

I need Notes for Gravitation, Circular Motion, Geostationary satellites and Momentum!

 

[Taci12]

Peace be upon you!
Can somebody explain mcq number 10 ,17 and 14 of:
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_s12_qp_13.pdf

And also mcq 17 of:
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_s10_qp_13.pdf
Thank You!

June 2012, p13
Question 10
Considering forces acting on the barrel:
resultant = weight of barrel - T
120a =120g - T (eqn 1)

a=acceleration of barrel, T=tension in rope

considering forces on man:

since man moves upwards, the net resultant force is upwards:
80a = T - 80g (eqn 2)

Both the man and the barrel have the same acceleration, as they are connected by the pulley system.

hence we add eqn 1 and eqn 2:
120 a + 80 a = 120g -T + T - 80g
200 a = 40 g
a = 0.2 g ms^-2


now we can use equation of motion : v^2 = u^2 + 2as

we are required to find the man's speed when he is level with the barrel, at this point, the displacement of the man(and of barrel btw) is 18/2, i.e it is 9 m. They meet halfway.

so: s=9, a= 0.2g, u = 0
replace in eqn of motion and you have the answer

Question 14

Upthrust is an upward force resulting from the difference pressures acting at the bottom and at the top of a body.

difference in pressure = pressure at bottom - pressure at top

since: pressure= force/area

force = pressure x area

in this case:

upthrust = difference in pressure x area

Hence the answer is C

We do not consider the weight as the upthrust is not a resultant force, it's just one of the forces acting on a body immersed in fluid, along with the weight and drag force.

Question 17:

First of all, find the mass: density = mass/volume
2.0 × 10^3= mass/ (0.60^3)
mass = 432 kg

The simply apply the formula for gravitational potential energy: P.E = mgh

June 2010, p13:

Question 17

efficiency = useful output energy/total input energy

The total input energy here is the work done by the force F in moving the car up the slope.
total input energy= Fs

The useful output energy is the increase in gravitational potential energy
useful output energy = mg Δh
Δh = vertical height covered by car = s sin α

useful output energy = m x g x (s sin α)

efficiency = m x g x (s sin α) / Fs

as "s" is common to both the denominator and numerator, it is eliminated, and the answer is D

 

[Taci12]

Physics AS or A-level help offered : http://www.xtremepapers.com/community/threads/physics-as-or-a-level-help-offered.22076/

 

[sweetsis]

PLS HELP ME WITH S09 P1 Q15....

 

[bogus]

i dont know how to do this ... plz help soon cuz i have an exam

 

[Gémeaux]

View attachment 19137
i dont know how to do this ... plz help soon cuz i have an exam

is the answer B?

 

[bogus]

d

is the answer B?

 

[Gémeaux]

d

pfft, i'd do it again properly.

 

[Gémeaux]

View attachment 19137
i dont know how to do this ... plz help soon cuz i have an exam

the total mass of X+Y is m+3m= 4m, so the total force F is F = 4ma
now, both X and Y are individual bodies
the mass of X is m, so Fx = ma
from the first equation we can also write F/4 = ma
this means that it takes in one-fourth of the total force in accelerating and exerts the remaining three-fourths on Y.

 

[bogus]

help!!

 

[bogus]

and this... i have an exam soon so urgent help needed

 

[Gémeaux]

bogus please post the answers too

 

[bogus]

help!!View attachment 19145View attachment 19146

a and d

 

[bogus]

and this... i have an exam soon so urgent help neededView attachment 19147

b

 

[Gémeaux]

and this... i have an exam soon so urgent help neededView attachment 19147

Force= change in momentum / time taken

 

[bogus]

Force= change in momentum / time taken

duhhh! i know but its final minus initial so the answer choice b and d are weird . A and c are wrong cuz they don't consider change in time. p2 is negative so the answer should be minus p2 minus p1 over change in time.... Can u answer my other mcqs as well

 

[Ding Ding]

13 A particle is in a uniform field. The particle experiences a force in the opposite direction to the
field.
Which field is the particle in, and on which property of the particle is the field acting?
field
property of particle on which the field acts
A electric charge
B electric current
C gravitational mass
D gravitational weight
Why the answer is A?