Physics: Post your doubts here!

[Error Syntax]

b (iii)

why isn't the mass in equilibrium at t=0? Since the weight + force applied to pull the mass = tension in the spring? the resultant force is zero.

It is because if you look at the the information in the question given then it states that at t=0 the mass was released....so it was the point when the resultant force does infact exist and it could have been 0 resultant force if the mass was released in any other time then t=0.

 

[shahzaib ihsan]

b (iii)

why isn't the mass in equilibrium at t=0? Since the weight + force applied to pull the mass = tension in the spring? the resultant force is zero.

If you see the upper part of question, (a), it states that mass is in equilibrium when the displacement of mass=0 . that means at 0 displacement, the weight is equal to the force created by the spring. Now at t=0, the mass has been released, the time t=0 represents the start of motion of the mass. At t=0, weight is NOT equal to the tension, so the mass moves upward. Hence there is resultant force acting on the mass, which causes it to move upwards.

 

[Bishnu Dev]

If you see the upper part of question, (a), it states that mass is in equilibrium when the displacement of mass=0 . that means at 0 displacement, the weight is equal to the force created by the spring. Now at t=0, the mass has been released, the time t=0 represents the start of motion of the mass. At t=0, weight is NOT equal to the tension, so the mass moves upward. Hence there is resultant force acting on the mass, which causes it to move upwards.

Seems i didn't read the question correctly.....

 

[Aishayasin]

Can anyone help me with part b(i)

 

[Bishnu Dev]

Can anyone help me with part b(i)

The diameter of the pulley is given so you can calculate the circumference. For 360 degree rotation, extension would be the circumference. For 8.5 degree, extension would be (Circumference/360) * 8.5

 

[Holmes]

explain?

 

[Bishnu Dev]

View attachment 62048
View attachment 62049View attachment 62052
explain?

b) i)
The phase shift between the waves (T1 and T2) is 60 degrees. Draw wave T2 5 small squares ahead of T1. Remember, both waves have same Period and Amplitude. To draw this, move the wave T2 to the right by 5 small squares. Check attachment 1.

ii) Now at time T=1 second, count the number of small squares down the X-axis until you reach the T1 wave. This is the displacement of the wave T1. Recall that 10 squares = A. Since it is 5 small squares below the time axis, it is negative. Displacement of T1 = -A/2 (Don't ignore the '-' Sign) Check attachment 2.

For wave T2, the displacement is above the time axis, so that's positive. Repeat the same counting process and you will get 5 small squares for wave t2 as well. Hence displacement = A/2

Resultant is sum of individual displacements, so that's zero.

 

[shahzaib ihsan]

b) i)
The phase shift between the waves (T1 and T2) is 60 degrees. Draw wave T2 5 small squares ahead of T1. Remember, both waves have same Period and Amplitude. To draw this, move the wave T2 to the right by 5 small squares. Check attachment 1.

ii) Now at time T=1 second, count the number of small squares down the X-axis until you reach the T1 wave. This is the displacement of the wave T1. Recall that 10 squares = A. Since it is 5 small squares below the time axis, it is negative. Displacement of T1 = -A/2 (Don't ignore the '-' Sign) Check attachment 2.

For wave T2, the displacement is above the time axis, so that's positive. Repeat the same counting process and you will get 5 small squares for wave t2 as well. Hence displacement = A/2

Resultant is sum of individual displacements, so that's zero.

in b1, how to know how many small squares ahead we have to plot? i seem to have forgotten the formula/method...

 

[shahzaib ihsan]

in b1, how to know how many small squares ahead we have to plot? i seem to have forgotten the formula/method...

np i get it now... so time period of the wave is 30 small boxes
phase difference = (360/timeperiod)x timeinterval difference, so: 60=(360/30) x time interval difference , so (60x30)/360 = time interval difference = 5, which means 5 small boxes ahead of it.

 

[ka2017]

Hi!

O/N 2009 P22, Q.1 I am having difficulty deciding how many significant figures or decimal places to use... For L = 92±1 cm, the percentage uncertainty is 1.09%. Shouldn't we write the final answer as 1%, because the smallest no. of sig fig in the given data L = 92±1 is one?

Thanks!

 

[Bishnu Dev]

Hi!

O/N 2009 P22, Q.1 I am having difficulty deciding how many significant figures or decimal places to use... For L = 92±1 cm, the percentage uncertainty is 1.09%. Shouldn't we write the final answer as 1%, because the smallest no. of sig fig in the given data L = 92±1 is one?

Thanks!

NEVER write the final answer in one significant figure or as an integer.

92 is two significant figure and the uncertainty is 1 which is usually quoted in one sf. You are writing the percentage uncertainty so you shouldn't keep it in 1 sf.

 

[Jamil Zaitouni]

Is it okay to write part 1 from P5 as bullet points?

 

[student2]

Pleasseee sm1 help

 

[Myaaa_20]

Hey, does anyone have worked solutions for paper 5, the latest ones ( from 2014 onward)?

 

[student2]

http://papers.gceguide.com/A Levels/Physics (9702)/9702_w15_qp_43.pdf

12 (b) i) Physicist cn u help pls?

 

[i_try9621]

View attachment 62066


Pleasseee sm1 help

 

[i_try9621]

http://papers.gceguide.com/A Levels/Physics (9702)/9702_w15_qp_43.pdf

12 (b) i) Physicist cn u help pls?

They are asking for the minimum bits needed to encode the sample (to convert from analogue to digital). You can see the maximum voltage here is 15mv which requires at least 4 bits, above 15mv such as 16mv, you will need at least 5 bits. So the minimum bits needed here is 4
Ans is 4

 

[i_try9621]

Should an oscilloscope be connected in parallel in a circuit or in series?

 

[sj0007]

Should an oscilloscope be connected in parallel in a circuit or in series?

It's always connected in parallel

 

[student2]

They are asking for the minimum bits needed to encode the sample (to convert from analogue to digital). You can see the maximum voltage here is 15mv which requires at least 4 bits, above 15mv such as 16mv, you will need at least 5 bits. So the minimum bits needed here is 4
Ans is 4

thnx soooo much.