PHYSICS PAPER 1 HELP!!!!

[supermagic]

9702_s03

q5,13,15,20,22,34,35

THX!

 

[beacon_of_light]

Q5: 3%...uncertainity is about 9.8. SO round of the value to the nearest tens.

Q13: resultant force is non-zero since two 20N forces have a resultant of 40N.... taking the center as axis of rotation, 20N forces have zero torque while 30N forces make a couple !

Q20: As the child lowers atmospheric presuure by 10%, new atm pressure is 10/100 x Po
applying the equation, pressure = density x g x h

1/10 Po = p xgxh
h = Po/10pg

Q22: Each spring bears a load of 1/3W ... F=Kx... K = F/x
K = (1/3W) / x

then...when a weight of 2W is hung, and one spring removed...
each spring now bears a weight of W ...

F= Kx
x = F/K ...substitute K's value
x*= W/ (1/3W)/x
x* = 3x

Q34: A variable resistor is present b/w P and Q... first consider the variable resistor to have a minimum resistance i.e 0 KV
using potential divider formula...
find V ... V = {0 / (0+10) } x 9
Now find V again taking 50KV...you'll get the range

Q35: When the distance b/w the plates is constant provided V also remains constant, electric field strength remains constant... E = V/d

Hope that helps you

 

[supermagic]

thx very much!!!!!!!
but i have a doubt!

in question 35, as distance increases, shouldnt E decreases?? shouldnt answer be A?? then y C???

 

[beacon_of_light]

Distance b/w the plates remains fixed. If the separation of plates was to increase, then Option C would be right...