Physics: Post your doubts here!

[Ab30657]

Can someone provide a detailed explanation on this qn, just used unitary method to get the Ans:B
Also how can the current in the ammeter be 0?

 

[troller]

Guyz i need some tips from you people...I will be giving maths and chemistry Accel in 19 may/june along with physics A2.......Please tell me when should i start preparing FOR AS syllabus as i have studied it last year.......And please give me tips how can i get best grades?

 

[troller]

Please tell me is it useful to Solve question given in DAVID SANG(PHYSICS ALEVEL BOOK)?what are the benefits of solving this??

 

[Jihoo Lee]

Hi guys.
Do I need to get A in every papers to get A* in total? My friend said that don't need to get every paper(1 to 5) to get an A, but to get an A*, I should not have any B or C in my component. Is he correct?

 

[studyingrobot457]

Hi guys.
Do I need to get A in every papers to get A* in total? My friend said that don't need to get every paper(1 to 5) to get an A, but to get an A*, I should not have any B or C in my component. Is he correct?

it depends on the total mark,
e.g
in m/j 2018, The threshold for A* in physics was 203/260
this was for p11,21,31,41,51

so let's suppose u g0t the following marks
p1 38/40 - which is A for the component
p2 28/60 - which is C for the component
p3 - 32/40 -which is A for the component
p4 - 92/100 -which is A for the component
p5 - 13/30 - which is C for the component

total : 203

thus u get A*

 

[hellodjfos;s'ff]

Please tell me is it useful to Solve question given in DAVID SANG(PHYSICS ALEVEL BOOK)?what are the benefits of solving this??

I have the book. The book is good for revision of most topics, but the questions in the book are really easy so no point in doing them. Go straight to past paper questions instead.

 

[hellodjfos;s'ff]

Hi guys.
Do I need to get A in every papers to get A* in total? My friend said that don't need to get every paper(1 to 5) to get an A, but to get an A*, I should not have any B or C in my component. Is he correct?

No, you don't need an A in every paper to get an A*. You may have a D in a component and still achieve an A*(of course that requires you to score exceptionally well in the other components). If you look at the grade thresholds for physics, you need to get a raw score of 177 to get an A and 203 for A* out of 260.

 

[studyingrobot457]

No, you don't need an A in every paper to get an A*. You may have a D in a component and still achieve an A*(of course that requires you to score exceptionally well in the other components). If you look at the grade thresholds for physics, you need to get a raw score of 177 to get an A and 203 for A* out of 260.

advice^: don't answer a question that has been answered already

 

[hellodjfos;s'ff]

advice^: don't answer a question that has been answered already

Haha relax dude, just tryna help out. I didn't even see your reply

 

[ZHANG XIN]

Can someone provide an explanation to part (b) of this question?

I'm confused by magnitude of gravitational potential. Gravitatioanl potential is a scalar quantity and it is always negative.
If scalar quantity has magnitude only, the magnitude of gravitational is also a negatvie value.

In the the examiner report, the magnitude of gravitational potential is a positive value. so the answer is Ep = -mφ

 

[Wâlèé Atèéq]

Can I get Topical P4 compiled with MS ?

 

[VinSmoke]

In p3 i haven't made the table outline, but have recorded all data. How much marks am i loosing?

 

[Asad.Babur]

In p3 i haven't made the table outline, but have recorded all data. How much marks am i loosing?

0. You weren't going to get outline marks, just make sure rows and columns are identifiable!

 

[Raheel327]

Q. A car of mass 1.2×10^3 kg travels along a horizontal road at a speed of 10 m/s. It then accelerates at 0.20 ms-2. At the time it begins to accelerate, the total resistive force acting on the car is 160 N. What total output is developed by the car as it begins the acceleration? A. 0.80 kW B. 1.60 kW C. 2.4 kW D. 4.0 kW.

Q. A railway locomotive pulling a train delivers a constant power of 2.0×10^6 W to the wheels. The resistive forces are constant at all speeds. The maximum speed that the train can achieve on a level track is 40 ms-1. What is the resultant force accelerating the train when it is traveling at 10 ms-1?
A. 5.0 kW B. 5.5 kW C. 20 kW D. 22 kW

 

[Hamnah Zahoor]

Q. A car of mass 1.2×10^3 kg travels along a horizontal road at a speed of 10 m/s. It then accelerates at 0.20 ms-2. At the time it begins to accelerate, the total resistive force acting on the car is 160 N. What total output is developed by the car as it begins the acceleration? A. 0.80 kW B. 1.60 kW C. 2.4 kW D. 4.0 kW.

F - R = ma
F - 160 = (1.2*10^3) (0.20)
F = 400

P = Fv
P = (400)(10)
p = 4000 W
P = 4.0 kW ( option D)

 

[Hamnah Zahoor]

Q. A railway locomotive pulling a train delivers a constant power of 2.0×10^6 W to the wheels. The resistive forces are constant at all speeds. The maximum speed that the train can achieve on a level track is 40 ms-1. What is the resultant force accelerating the train when it is traveling at 10 ms-1?
A. 5.0 kW B. 5.5 kW C. 20 kW D. 22 kW

What is the answer for the above question?
And I guess you have typed in the question wrong because the question asks for the resultant force but the units used in the option are for power.

 

[Raheel327]

Its D, 4.0 kW.
The correct second question options:
A. 5.0×10^4 N B. 1.5×10^5 N C. 2.0×10^5 N
D. 2.5×10^5 N
1.5×10^5 N is the correct answer.

 

[Raheel327]

Do we always use the resultant force only to calculate power, in the formula p=fv?
And, in the first question the car later accelerates. Wouldnt that change its speed so it's no longer 10?

 

[Hamnah Zahoor]

Q. A railway locomotive pulling a train delivers a constant power of 2.0×10^6 W to the wheels. The resistive forces are constant at all speeds. The maximum speed that the train can achieve on a level track is 40 ms-1. What is the resultant force accelerating the train when it is traveling at 10 ms-1?
A. 5.0 kW B. 5.5 kW C. 20 kW D. 22 kW

When the train is at its' maximum speed the acceleration is to be considered zero. Which means the resultant force acting on the train is zero. In order to calculate the force acting:
P = Fv
2*10^6 = F (40)
F = 50,000 N
Forward force is 50,000 and the resistive force is also 50,000 N which makes the total resultant force equal to zero.
It is said in the question statement that the resistive force is constant at all speeds thus at 10 ms^-1 Rf= 50,000 N
P = Fv
2*10^6 = F(10)
F = 2*10^5
Resultant force equals to forward force minus resistive force
(2*10^5)-(50,000)
1.5*10^5 N

 

[Hamnah Zahoor]

Do we always use the resultant force only to calculate power, in the formula p=fv?

No the forward force is used and also in the question I have used F = 400 N not the resultant which is 400-160= 240 N

At the time when acceleration begins the speed is 10 ms^-1 .