Physics: Post your doubts here!

[Mathemagical]

View attachment 54615
Why 2 significant figures... why not 3??

Actual uncertainties are usually written to 1 significant figure. In this case, the actual uncertainty is 9.8298, so we round it off to 10. Since the significant digit is in the tenths, the calculation would be written as 330 m/s.

 

[Mathemagical]

View attachment 54616
How??

We know that the blocks must have the same acceleration. Applying Newton's Second Law to the entire system, we get

F = 4ma
a = F/4m

Fy = myay
Fy = 3m (F/4m)
Fy = 3F/4

 

[Mathemagical]

View attachment 54617
Why B?
Don't the wheels exert a force shown by red?
So shouldn't the force by road be D (shown in blue)?
So why is it B??

You forgot the vertical contact force exerted by the weight on the road. According to Newton's 3rd Law, the road exerts the same force but in the opposite direction. Therefore, the answer is B, which is the resultant of the 2 forces.

 

[nehaoscar]

Read the green writing first

 

[nehaoscar]

What are the correct estimated values for A,B and C?

 

[Mahnoorfatima]

https://docs.google.com/viewerng/vi...wp-content/uploads/2012/11/9702_s14_qp_12.pdf
Q35 anyone. It's a pretty simple question but idk I can't solve it.

 

[Mathemagical]

Read the green writing first

I wouldn't call spacing between liquid molecules "far", it is only a little less closely packed than molecules in a solid.

 

[Mathemagical]

What are the correct estimated values for A,B and C?

Frequency of radio wave: 100 GHz
Mass of atom: 10^-27 kg
Young Modulus of a metal: 200 GPa

 

[nehaoscar]

I wouldn't call spacing between liquid molecules "far", it is only a little less closely packed than molecules in a solid.

So the rest seem alright yeah?

 

[Mathemagical]

So the rest seem alright yeah?

Yes, they do

 

[abruzzi]

Hey,

Could someone please show me how to work out the voltage and current across R1 and R2 respectively? Thanks!

 

[nehaoscar]

Why can't it be A??
A shows that velocity is increasing steadily, so constant acceleration so air resistance negligible right?
So why not A??

 

[nehaoscar]

Hey,

Could someone please show me how to work out the voltage and current across R1 and R2 respectively? Thanks!

It's a series circuit, so the current will be the same all around
Add up the emf of the batteries taking in note their directions
(so add up the ones facing one direction and subtract it from the others facing the other direction)

This gives total emf = 6V
Total resistance = 1000 + 100 ohms = 1100

Current = V/I
= 6/1100
= 5.5mA

V across R1 = I x R1
= 5.5mA x 100
= 0.55V

I across R2 = as I said earlier it's a series circuit, so the current is same in all components
= 5.5mA (as calculated above)

 

[nehaoscar]

Why C?? Why multiply it by A?

 

[Mathemagical]

Hey,

Could someone please show me how to work out the voltage and current across R1 and R2 respectively? Thanks!

Taking clockwise as the positive direction,
e.m.f = 1.5-1.5-1.5+1.5+1.5+1.5+1.5+1.5+1.5-1.5 = 6V

Total resistance = 1100 ohm

Current through R2 = V/R = 6/1100 = 5.5mA.

Voltage across R1 = (100/1100)*6 = 0.55V

 

[nehaoscar]

How to do??

 

[Mathemagical]

View attachment 54620
Why C?? Why multiply it by A?

Upthrust is a force. Force = Pressure*Area.

 

[nehaoscar]

Why not B?

 

[Mathemagical]

View attachment 54619
Why can't it be A??
A shows that velocity is increasing steadily, so constant acceleration so air resistance negligible right?
So why not A??

It cannot be A because the graph levels out, indicating constant velocity. If air resistance were negligible, the acceleration would always be equal to 9.81 m/s2 and the velocity would always be increasing constantly.

 

[Mathemagical]

View attachment 54622
Why not B?

B shows a straight line. The path must always be a curve.