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PAPER 1 phisics Multiple choise doubts
- Thread starter 1992
- Start date
for q.7 we will count da waves
that is coming about 8.5 waves
then we will divide it by 60 ms
becx for 1 box it is 10 ms so we've got 6 boxes so 60 ms
and so we get 141.7 waves/sec
as they've askd approximate so itx B
140 waves/sec
in other words 140 Hz
that is coming about 8.5 waves
then we will divide it by 60 ms
becx for 1 box it is 10 ms so we've got 6 boxes so 60 ms
and so we get 141.7 waves/sec
as they've askd approximate so itx B
140 waves/sec
in other words 140 Hz
for q.11 da formula ov elastic collision is applied
that is;
Relative speed of approach = relative speed of departure
Ua - Ub = Vb - Va
then according to da directions v put da signs lyk:
(+ Ua) - (- Ub) = (+ Vb) - (+ Va)
so finally v get:
Ua + Ub = Vb - Va
that is part A
that is;
Relative speed of approach = relative speed of departure
Ua - Ub = Vb - Va
then according to da directions v put da signs lyk:
(+ Ua) - (- Ub) = (+ Vb) - (+ Va)
so finally v get:
Ua + Ub = Vb - Va
that is part A
for q.18 we'll use two formulas;
firstly: P.E = m.g.h
so the energy is coming
P.E = (1.3 x 10^9) x (10) x (2)
P.E = 2.6 x 10^10
now we will calculate power by formula;
P = E/t
as da tym is 1 day so we will convert it to sec to get
t = 24 x 60 x 60
t = 86400 s
now putting in da values
P = (2.6 x 10^10) / (86400)
P = 300.9 kW
so da ans is D
firstly: P.E = m.g.h
so the energy is coming
P.E = (1.3 x 10^9) x (10) x (2)
P.E = 2.6 x 10^10
now we will calculate power by formula;
P = E/t
as da tym is 1 day so we will convert it to sec to get
t = 24 x 60 x 60
t = 86400 s
now putting in da values
P = (2.6 x 10^10) / (86400)
P = 300.9 kW
so da ans is D
for q.19;
initially da twig has P.E.
as mass is unknown so we will take it as m
so initially:
P.E. = m.g.h
P.E.= (200).(10).(m)
P.E. = 2000m (J)
as 40% is lost as heat so we will subtract it lyk:
first calculate 40% of 2000m
its = 2000m x 40/100 = 800m
as dis 800m is lost so we will subtract it from 2000m
so we will get 1200m (J)
now as dis much energy is converted to kinetic energy so
1200m = (0.5).m.v^2 -(formula for kinetic energy)
m will cancel out so we will get
v = 49 m/s
so da ans is C
initially da twig has P.E.
as mass is unknown so we will take it as m
so initially:
P.E. = m.g.h
P.E.= (200).(10).(m)
P.E. = 2000m (J)
as 40% is lost as heat so we will subtract it lyk:
first calculate 40% of 2000m
its = 2000m x 40/100 = 800m
as dis 800m is lost so we will subtract it from 2000m
so we will get 1200m (J)
now as dis much energy is converted to kinetic energy so
1200m = (0.5).m.v^2 -(formula for kinetic energy)
m will cancel out so we will get
v = 49 m/s
so da ans is C
for q.35
as we increase the resistance of varible resistor
so the voltage across it will also increase
this means dat the voltage across XY will decrease
(as they r in series and voltage divides proportionally b/w the resistors according to their resistances)
so v r left wd either option C or D
now as the voltage across XY decreases the voltage across XN will also decreases
for zero deflection we have to increase the value of voltage to the same value as it was before
we will get that value near Y
becux near X the voltage will further decrease as length is directly proportional to pd across it
so our ans is D
as we increase the resistance of varible resistor
so the voltage across it will also increase
this means dat the voltage across XY will decrease
(as they r in series and voltage divides proportionally b/w the resistors according to their resistances)
so v r left wd either option C or D
now as the voltage across XY decreases the voltage across XN will also decreases
for zero deflection we have to increase the value of voltage to the same value as it was before
we will get that value near Y
becux near X the voltage will further decrease as length is directly proportional to pd across it
so our ans is D
- Messages
- 37
- Reaction score
- 7
- Points
- 0
the formula is..
R=$L/A
r=resistance
$=resistivity
L=length
A=area
now...R=V/I
so accordig to the equation.....V is directly propotional to the length
R=$L/A
r=resistance
$=resistivity
L=length
A=area
now...R=V/I
so accordig to the equation.....V is directly propotional to the length
1992 said:
The emf of the battery is 2 V
in paralell the voltage will remain same so pd across each branch is 2 V
there are 3 resistors connected in series in each branch
we will calculate the voltage dat each resistor will use
to do this we will first calculate the total resistance in the whole ckt
Total R = 7.5 ohms
Now we will calculate the value for total current
I = V/R
I = 2/7.5
I = 0.267 A
Now we will calculate current in each branch
As the resistance in each branch is the same -i.e- 15 ohms
so current will divide equally in both branches
in 1 branch;
I = 0.267/2
I = 0.133 A
Now we will calculate the voltage each resistor will take
V = IR
V = 0.133 x 5
V = 2/3 V
So at X the Voltage will be
V = 2 - 2/3
V = 4/3 V
and at Y
V = 2 - (2/3) - (2/3)
V = 2/3 V
so to get the pd across X and Y
we will subtract voltage at X from Voltage at Y
so we get A as the answer
I hope this extensive explanation helps!!!
