Physics: Post your doubts here!

[princess Anu]

What exactly is wrong in option B?

 

[princess Anu]

Your arrow doesn't start at the pivot. Look at A and C, F is at an angle to the line from the pivot in C but it is closer to 90 degrees in A, so there will be a larger moment in A.

help...ans is B ..

 

[DaniyalK]

Someone plzz help me on this thanks in advance
Q9 and Q10... I didnt get it :/
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This is a repeat qstn but i still didnt get it :/
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Any quick way to calculate the energy except for counting boxes... Its time consuming...
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View attachment 54909
I didnt get it.... Why isnt it C? I mean the gradient of I/V should be highest so that V/I should be lowest and R=V/I so R should be lowest...
View attachment 54910
View attachment 54911

9: initial momentum = final momentum
m(2v) + 3m(-v) = 4m(vf)
vf = -v/4
10: Just move the arrows around in your head without changing their direction to make a triangle. D is the only way you can make the triangle with the arrows in their original direction.
12: Take the pivot at the point where the ladder meets the wall. All distances must be perpendicular to the forces. F is perpendicular to h and W is perpendicular to a/2a. Equate the clockwise and anticlockwise moments.
21: Just draw a triangle with base .3 m and height 17 N. Area under the triangle is 2.6 but obviously the graph has less area than this so A is the only possible option.
30: Before the switch is opened, 2 and 3 are in parallel, so their resistance is less and their pd is less, while 1's pd is high. when the switch is opened, it becomes a series circuit, so the pd of 2 increases and 1's share of the pd decreases ( think of it as a potential divider circuit)
34: Smallest resistance is at the point where the ratio of V to I is least.
38: Speed of alpha particle is about 5% of the speed of light

 

[princess Anu]

How can we estimate volume of an adult head?
any tip for the estimations please?

 

[Ahmed Aqdam]

Do we always quote uncertainty to 1 sig fig or it depends on the values given?

Uncertainty in a measured quantity is always to 1 significant figure.

 

[princess Anu]

ans is c help

 

[BhaiArshad]

How can we estimate volume of an adult head?
any tip for the estimations please?

take 15 cm scale.
measure your head dimensions.
fFind volume
Profit..???

 

[DaniyalK]

help...ans is B ..View attachment 54924

1 = sqrt[(1+cosx)^2 + (sinx)^2]
x = 120

 

[Ahmed Aqdam]

How can we estimate volume of an adult head?
any tip for the estimations please?

Use this file.
You can also estimate by (4pi/3)*r^3. Use r as 7-9 cm.

 

[BhaiArshad]

ans is c help

Tension in XY = 4N
Tension in XZ = 4N

Extend the line of P so that it crosses through the troangle. It forms 2 right andle triangles. ANgle between Perpendicular and Hypotenuse(XY,XZ) can be found by Sin Theta = 40/50
angle is 53.1

Force of XY in direction P = 4 cos (53.1) = 2.4
Force of XZ in direction P = 4 cos (53.1) = 2.4
Total Force in direction if p = 2.4 +2.4 =4.8 C

 

[nehaoscar]

How and why A??

 

[princess Anu]

1 = sqrt[(1+cosx)^2 + (sinx)^2]
x = 120

sqrt[(1+cosx)^2 + (sinx)^2]
How did u come up with this.. explain pls

 

[princess Anu]

how B
:s

 

[BhaiArshad]

View attachment 54927
How and why A??

The graph is a decreasing gradient curve.
you can see at the end there is less change in angle for an increase in current. That means for high current there will be less deflection. Less desflection means that the values will be close together at the end. at the beginning there is more change in angle per unit change in current. so equaldeflctlion for equal change in current.

 

[asadalam]

\
how B?

 

[DaniyalK]

sqrt[(1+cosx)^2 + (sinx)^2]
How did u come up with this.. explain pls

Pythagoras... Resultant^2 = (sum of X components)^2 + (sum of Y components)^2
When you consider option B
F2:
X comp. = 1cosx
Y comp. = 1sinx
F1 only has an x component of 1

 

[BhaiArshad]

how B
:sView attachment 54928

Fom 12:00 to 12:30 distance coveref is 100 miles
From 12:30 to 1:30 distance covered is 200 miles.
Total distance covered = 300 mile so outside of range of cambridge
Remaining distance to covere = 80 mile but we only have fuel for another 50 miles since fuel for 300 miles is used up so emergency langding.

 

[muhammadali233]

how B?

asap bro

 

[Ahmed Aqdam]

\
how B?

It is directly proportional to l and also inversely proportional to l^2.
So in overall equation it is proportional to l/l^2. Simplify to get 1/l.

 

[asadalam]

Could you elaborate?