Physics: Post your doubts here!

[princess Anu]

View attachment 54041

can anyone answer plzzzz?????

basically here the voltmeter acts as a resistor. So consider it as a resistor
so when its resistance is 1K ohms , the voltage divides in 1:1 ratio
but when its resistance increases to 1000000 ohms, which is huge compared to 1000 ohms, therefore almost all the voltage goes to the voltmeter .. as in a series circuit current is constant and v is proportional to r

 

[princess Anu]

what does o.5mm/rev imply here?

 

[anasaziz18]

HELP !! View attachment 54038

Since it is a parallel circuit, the pd across the (variable r. and a resistor in series with it) and the other single resistor(rightmost) is the same (i.e the same value as the emf of the battery). Resistance of the rightmost resistor is also unchanged. Hence V/R=I is unchanged.

When the resistance of vr is increased, pd across it will increase and reading on the voltmeter will therefore decrease.

 

[nehaoscar]

Help please!?

 

[nehaoscar]

I thought X and Y is actually the plastic region??
as shown here:


But then the answer is D :/ ???

 

[princess Anu]

Since it is a parallel circuit, the pd across the (variable r. and a resistor in series with it) and the other single resistor(rightmost) is the same (i.e the same value as the emf of the battery). Resistance of the rightmost resistor is also unchanged. Hence V/R=I is unchanged.

When the resistance of vr is increased, pd across it will increase and reading on the voltmeter will therefore decrease.

but doesn't I depend on the ratio of resistances? for example if the emf is 10
variable resistor & the resistor with voltmeter have a combined resistance of 50 while the resistor on the right 20
in that case I will be = 10/ 14= O.71
but if now the variable resistor's resistance has increased so that the combined resistance now is 70
now I= 10/ (70*20/20+70) ,I= 0.6 :/

 

[princess Anu]

 

[princess Anu]

ans is B

 

[eliyeap]

View attachment 54058 ans is B

KE= PE+KE
1/2(m)(28)^2=m(g)(22)+1/2(m)(v)^2
The initial KE is converted into PE when it leaves the exit road since the road is 22m higher than the motorway. Since they ask the final speed this means that not all KE is converted into PE, hence there is remaining KE

 

[eliyeap]

View attachment 54056

They say that wheel friction is constant throughout the motion. Therefore, from the graph when there is 0 velocity, the wheel friction is 8kN.
The total resistive force (wheel friction+ air resistance) at v=200 is 40kN.
Ratio= 32k/4k= 8

 

[eliyeap]

View attachment 54050
Help please!?

Is it C?

 

[nehaoscar]

Is it C?

Yess! Please could you explain?

 

[nehaoscar]

Why and how is it A?

 

[princess Anu]

Q8 pls

 

[princess Anu]

why not C?

 

[princess Anu]

.

 

[nehaoscar]

Can someone please give me notes on this states of solid liquid gas and evaporation boiling condensation melting freezing etc... because i get confused with these questions and i can't find it in the text book :/

 

[nehaoscar]

Why not A ?

 

[eliyeap]

Yess! Please could you explain?

It's evaporation because evaporation is a process which depends on the velocity of the water molecules. If the molecules at the surface possess enough energy then they are able to escape the forces that hold the molecules together and then escape as vapour. But the question states that all the molecules have the same speed, hence evaporation cannot occur

 

[eliyeap]

View attachment 54068
Why not A ?

Voltmeter normally has very high resistance to make sure that current doesn't flow through it when it measures the pd across an object. It cannot be A because since the voltmeter is connected in series , the current would have to pass through the voltmeter before it can reach the ammeter. Very high resistance so no current passes through.