iGCSE EDEXCEL PHYSICS DISCUSSION 2012

Force stays the same surely?
I said pressure decreases because force stays the same but area increases, and p=F/A

What did everyone write for the terminal velocity question and the stupid smoke detector/radon question?

i'm not sure though!!

I just though force would remain constant because it is the weight of the 8 coins, and thus the weight on the whole table wouldn't change

EDIT:
The questions were what would happen if only 2 parachutes were opened instead of 3 etc, and why is radon gas more harmful than the solid in smoke alarms

stupid smoke detector/radon question?

yeah, but in the third part of the question whats was the effect on the pressure? I put pressure decreases as force decreases and as area increases...Am i right?

radon gas is present in the atmosphere and is in direct contact with people. Americium is in a smoke alarm and is prolly covered by a metal case. Alpha cannot penetrate paper and therefore cannot penetrate the case.

I wrote sumthing along those lines...

yeah, but in the third part of the question whats was the effect on the pressure? I put pressure decreases as force decreases and as area increases...Am i right?

i put force decreases...because in the previous pic the coins were on top of each other while in the 2nd pic they were all spread out...in the 1st pic each coin would exert a force on the other so the force kind of accumulates...i'm not sure...i just used logic...

if only 2 parachutes were opened the the time taken to reach constant wud be longer as the initial air resistance would be less and the acceleration would be more...but in the pic with 3 parachutes...the air resistant is more than the air resistance in the 2nd pic...so less time to reach constant velocity.

Radon gas is more harmful because it is present in air. Air is present everywhere. Smoke alarms are only activated when there is a fire...so it rarely occurs...but radon is present everywhere at everytime

how do u know its covered in a metal case!

Force doesnt decrease;stays the same.
Area increases and since pressure is inversely proportional to area, pressure decreases.

if only 2 parachutes were opened the the time taken to reach constant wud be longer as the initial air resistance would be less and the acceleration would be more...but in the pic with 3 parachutes...the air resistant is more than the air resistance in the 2nd pic...so less time to reach constant velocity.

Hey was the question asking about the time they take to reach terminal velocity or the constant speed it travels after terminal velocity???

That's what I wrote- more time taken to reach terminal velocity! BUT apparently it is that terminal velocity would be greater? So in the end it would be going faster with only two parachutes as opposed to 3- which does make sense

Hey was the question asking about the time they take to reach terminal velocity or the constant speed it travels during terminal velocity???

Force stays the same surely?
I said pressure decreases because force stays the same but area increases, and p=F/A

I didn't do that! I found the power needed by dividing 6000000 by 180s (3 minutes) and it was more than 24kW so I said you needed an extra power source oops

Terminal velocity in the one with 2 chutes is greater because the drag equals weight after a longer time when the speed is greater. It was for 2 marks, most prolly, 1 for longer time to achieve terminal velocity and 1 for greater terminal velocity.