Physics: Post your doubts here!

[syed1995]

Asalam-o-Alaikum once again..!
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_w11_qp_21.pdf
Question 3ci.. when they ask us to calculate change in momentum...is it like mv - mu or mu - mv ?
thanks a bunch..!

final momentum - initial momentum ..
mv - mu
m(v-u)

 

[SalmanslK]

Physics A2..June 05 P4 Q1 .

' State The Origin Of Centripetal force? '

the Earth is orbiting the sun in this question...what is the origin anyone?

 

[daredevil]

may june 2012 p22 Q3 and Q7

 

[Tabi Sheikh]

so in every question of this type, are we supposed to use πd^2/4 for area?!

not in every question but where the diameter is given .....

 

[abruzzi]

http://papers.xtremepapers.com/CIE/...and AS Level/Physics (9702)/9702_w03_qp_2.pdf
I'm having a problem with qn no. 3c (i) and (ii part 2). Could someone please explain the direction of forces in the strings and why the torque is equal to the moment?
Thanks

 

[Tabi Sheikh]

may june 2012 p22 Q3 and Q7

Q3ii)since there is no accel. therefore log is said to be in equilibrium i.e. not external force acting related with newtons first law
Q3 iii) weight component downward + frictional force equal to tension
Q3 iv) since friction is involved there will be loss of energy due to friction

 

[Tabi Sheikh]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_w03_qp_2.pdf
I'm having a problem with qn no. 3c (i) and (ii part 2). Could someone please explain the direction of forces in the strings and why the torque is equal to the moment?
Thanks

since the disc remains in equilibrium therefore he forces are as shown

 

[Tabi Sheikh]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_w03_qp_2.pdf
I'm having a problem with qn no. 3c (i) and (ii part 2). Could someone please explain the direction of forces in the strings and why the torque is equal to the moment?
Thanks

since the moment must be same for object to be in equilibrium therefore its 45 Nm from previous part

 

[abruzzi]

View attachment 24711
since the disc remains in equilibrium therefore he forces are as shown

Thanks.. but isn't it the tension force that should be indicated?

 

[littlecloud11]

Physics A2..June 05 P4 Q1 .

' State The Origin Of Centripetal force? '

the Earth is orbiting the sun in this question...what is the origin anyone?

The gravitational force of the Sun.

 

[Tabi Sheikh]

Thanks.. but isn't it the tension force that should be indicated?

it is the tension f the string but they asked the direction of the force not the type

 

[Warrior66]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_s12_qp_22.pdf question 2, part b?
gary221 littlecloud11
thanks a bunch!

 

[SalmanslK]

J 06 Q2 b part (ii)

 

[littlecloud11]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_s12_qp_22.pdf question 2, part b?
gary221 littlecloud11
thanks a bunch!

While moving downward from A to the ground the velocity changes from 8.4 to 13 m/s. The time elapsed is .47 sec. There is a time delay of .02 sec during which the ball is in contact with the ground and the velocity drops from 13 m/s to 4.2 m/s this is shown by the sharp fall in the graph. As the ball begins to move upwards the velocity is now in the opposite direction or negative. You can calculate the time taken for the ball to come to rest by using v = u + at
0 = 4.2 - 9.8t
t =.42 sec.
So the ball moves for the further .42 sec before it comes to rest.

 

[gary221]

Warrior66, seems i ws a bit late to the party!!


sm1 already answered thm!!

 

[gary221]

Hey, just one question- in the potential divider why did you take R1 to be 1000 ohms? Shouldn't 125 be taken as R1, since the voltage that passed through the strain gauge is the voltage is passes through the op- amp?

no, its not like tht... see the total voltage is divided btw the 2 components in the ratio of thr resistances ie the component with more resistance gets more voltage..
So, the strain gauge gets part of the voltage (0.5) n allows the REST OF THE VOLTAGE to pass thru... ie it keeps 0.5 V, n lets 4 V pass thru..
n this remainder(4 V) is wht passes thru the op-amp..

Hope u gt it!!

 

[Warrior66]

View attachment 24727

While moving downward from A to the ground the velocity changes from 8.4 to 13 m/s. The time elapsed is .47 sec. There is a time delay of .02 sec during which the ball is in contact with the ground and the velocity drops from 13 m/s to 4.2 m/s this is shown by the sharp fall in the graph. As the ball begins to move upwards the velocity is now in the opposite direction or negative. You can calculate the time taken for the ball to come to rest by using v = u + at
0 = 4.2 - 9.8t
t =.42 sec.
So the ball moves for the further .42 sec before it comes to rest.

Thank you so much littlecloud11!!

 

[Warrior66]

Warrior66, seems i ws a bit late to the party!!


sm1 already answered thm!!

it's no prob gary221!

 

[abcde]

Does anyone have an explanation for Q3. (b) (i) 1 and (b) (ii) 1 ?
Thank you in advance./

 

[hassankhan]

plz someone help me how to do uncertainity problems.... i never get thm correct