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A-Level Physics Paper 1 doubts (MCQ)

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NidZ- Hero:

--- Quote from: Ghost Of Highbury on June 05, 2011, 07:25:12 am ---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




--- End quote ---



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:

--- Quote from: NidZ- Hero on June 05, 2011, 07:48:22 am ---

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


--- End quote ---

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:

--- Quote from: NidZ- Hero on June 05, 2011, 08:28:08 am ---Question 12 and Question 22? http://www.xtremepapers.me/CIE/Internat ... 2_qp_1.pdf
Please explain.



THANKS

--- End quote ---

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

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