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Oxford PAT help specimen paper

http://www.physicsandmathstutor.com/pat/
for the specimen solutions for question 12 it says If the source is removed entireiy then the count rate remains the same
I know this is background radiation but is background radiation alpha beta and gamma. I know there is cosmic rays and radon gas which is radioactive but are these radioactive due to the emission of alpha beta gamma particles?
Also why is the answer not alpha and beta

For question 13, why would it fall and slow down?- what physics explains this

How do u do question 17?
For question 18, is the acceleration 10 for the whole of the journey and isn't air resistance taken into account?
For question 19, do u assume that the voltage remains constant?

For question 21, why is the answer that?
For question 22, why is R' on there?
For question 24, why is
'When the battery is connected with * to C and - to A no current is measured'
given because i can't see its relevance and why does the question say
with a 9 V battery connected in series when all 4 bullet points say connected in parallel essentially?
For question 24c, wouldn't no current flow because the diode would have infinite resistance in that direction?
for q24d, why doesn't current flow through the capacitor and why wasn't it flowing through the diode before?
For q25b, why are the tension arrows both ways on the diagram and what does it mean that the pulley system gives mechanical advantage?
for 25c, why does the counterweight move half as far and isn't it asking for the average speed of the whole system?

Thanks and any help at all is appreciated!
(edited 8 years ago)
13 - have you seen a free body diagram for a plane in level flight at a constant velocity?



drag is caused by the planes airspeed - increasing speed means increasing drag, reducing speed means reducing drag
lift is caused by the air flowing over the planes wings - increasing speed means increasing lift, reducing speed speed means reducing lift

for level flight at a constant speed the forces must be balanced i.e. sum to zero

if the amount of thrust is reduced by a sudden engine failure then the amount of drag will no longer balance the amount of thrust and the plane will decelerate until the amount of drag is in balance with the new amount of thrust.

so what happens to the lift of the plane while it's speed is reducing and what is the effect of this on it's altitude?
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runny4
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Original post by Joinedup
13 - have you seen a free body diagram for a plane in level flight at a constant velocity?



drag is caused by the planes airspeed - increasing speed means increasing drag, reducing speed means reducing drag
lift is caused by the air flowing over the planes wings - increasing speed means increasing lift, reducing speed speed means reducing lift

for level flight at a constant speed the forces must be balanced i.e. sum to zero

if the amount of thrust is reduced by a sudden engine failure then the amount of drag will no longer balance the amount of thrust and the plane will decelerate until the amount of drag is in balance with the new amount of thrust.

so what happens to the lift of the plane while it's speed is reducing and what is the effect of this on it's altitude?

reducing speed means reducing lift and so it will decrease in altitude. thanks i get it. if you have time please can u answer some of my other questions?

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