A-Level Physics Paper 1 doubts (MCQ)

[NidZ- Hero]

Im not sure about variant 1. The torque is obviously 4.5Nm
{Tension = Torque/diameter = 3/0.1 = 30
  Torque = tension*diameter = 30*0.15=4.5}

Although, i'm not sure why the tension is 60. Maybe, because the lower belt has no tension, and for a torque two forces acting in opposite directions
are required, I guess, the tension in the lower belt is transferred to the upper belt which adds up to 60 (30+30).

The projectile one is easy
Let's say the initial velocity of the projectile is u
The velocity at highest point is horizontal with velocity ucos 45

KE = 0.5m*(ucos45)^2 = 0.5m*u^2*0.5
0.5E

0.5m*(ucos45)^2 = 0.5m*u^2*0.5 i gt the the answer till here how do yu simplify so that yu get 0.50E

ya i know even i gt tension as 30 But the answer is 60

idk y so askin

THANKS

[Ghost Of Highbury]

0.5m*(ucos45)^2 = 0.5m*u^2*0.5 i gt the the answer till here how do yu simplify so that yu get 0.50E

ya i know even i gt tension as 30 But the answer is 60

idk y so askin

THANKS

They've said that the kinetic energy initially is E, which is E = 0.5mu^2 (substitute this E in 0.5m*u^2*0.5)
SO u get 0.50E

[NidZ- Hero]

Question 12 and Question 22? http://www.xtremepapers.me/CIE/Internat ... 2_qp_1.pdf
Please explain.



THANKS

[elemis]

Question 12 and Question 22? http://www.xtremepapers.me/CIE/Internat ... 2_qp_1.pdf
Please explain.



THANKS

The link is broken.

[NidZ- Hero]

 A steel string on an electric guitar has the following properties.
diameter = 5.0 × 10^–4m
Young modulus = 2.0 × 10^11Pa
tension = 20 N
The string snaps, and contracts elastically.
By what percentage does a length l of a piece of the string contract?
A 5.1 × 10^–4%
B 5.1 × 10^–2%
C 1.3 × 10^–4%
D 1.3 × 10^–2 %
I know the Answers but i wanna Know hw do yu get them
Pls Show the workin



THANKS

[NidZ- Hero]

The link is broken.

thanks ari i gttta the answer

[Ghost Of Highbury]

 A steel string on an electric guitar has the following properties.
diameter = 5.0 × 10^–4m
Young modulus = 2.0 × 10^11Pa
tension = 20 N
The string snaps, and contracts elastically.
By what percentage does a length l of a piece of the string contract?
A 5.1 × 10^–4%
B 5.1 × 10^–2%
C 1.3 × 10^–4%
D 1.3 × 10^–2 %
I know the Answers but i wanna Know hw do yu get them
Pls Show the workin



THANKS

is it B?

E = stress/ strain = FL/A*e
2.0 * 10^11 = 20l/(1.96*10^-7)e
e = 20l/12500pi
%change = e/l *100 = (20l/12500pi)/l *100 = 5.1*10^-2

[NidZ- Hero]

Yeah but how

[Ghost Of Highbury]

Yeah but how

check my previous post again (EDIT)

[NidZ- Hero]

is it B?

E = stress/ strain = FL/A*e
2.0 * 10^11 = 20l/(1.96*10^-7)e
e = 20l/12500pi
%change = e/l *100 = (20l/12500pi)/l *100 = 5.1*10^-2

highbury.. how did yu get e = 20l/12500pi   

where did yu get 12500pi  from 

[Malak]

highbury.. how did yu get e = 20l/12500pi   

where did yu get 12500pi  from 

Check attachment:

Hope you get it...