Physics: Post your doubts here!

[hela]

13,16,25,31

thanks a lot can you solve these

 

[hela]

can you solve these

 

[Abu mota]

please solve these 3 question

7. idk really.
8. D, because it is a rule if two particles of the same mass collide elastically then they interchange their velocities.
9. C , because young modulus is the same as long as the material is the same, and since they are both steel so the young modulus wont change.
10. D, because I is inversely proportional to x^2 which means that from the equation I is directly proportional to a^2 , a^2 is inversely proprtional to x^2 which means a is inversely proprtional to x, so if we double x we halve the amplitude. 8/2= 4 which is D.

 

[Abu mota]

13,16,25,31

13. A, because you have to consider the weight of the ruler which is 50N as it is a uniform ruler it must act at 1.5 ( half 3) which is 0.5 from the pivot 0.5x50=1xW (clockwise moment=anti-clockwise moment) W=25N
16. B, as there is no loss of energy to the surroundings as heat as there is no air resistance, the total energy of the ball will be constant.
25. A, always when u do this question move in the opposite direction to the energy travel, u will find that if u moved this way P will move downwards but as Q is maximum it will stay stationary (also for ur information minimum point stays stationary as well)
31.D, R is inversely proportional to d^2 so if u double d u will quarter the resistance at P, but as the question wants in terms of current then it will be 4 at P (as R is incersely proportional to current)

 

[Abu mota]

Hela:
for question 7 it might be because at first the total kinetic energy is 1/2 mv^2 and after that we have double the mass which mean kinetic energy is mv^2
as Ek= 1/2mv^2 then mv^2=2Ek then as we have two masses the kinetic energy is spread on both of them so 2Ek/2 will give Ek each and so there is no change in kinetic energy.
NOTE: imnot sure about the way i got the answer, i dont think it is correct.

 

[salvatore]

Aaaahhh, now i get it.. Thank you so muchh!! But what if we have constant velocity increase in a VELOCITY-TIME GRAPH, can we use the formula (a=v-u/t)?

Yeah.. that is possible. Ur welcome!

 

[Tkp]

13. A, because you have to consider the weight of the ruler which is 50N as it is a uniform ruler it must act at 1.5 ( half 3) which is 0.5 from the pivot 0.5x50=1xW (clockwise moment=anti-clockwise moment) W=25N
16. B, as there is no loss of energy to the surroundings as heat as there is no air resistance, the total energy of the ball will be constant.
25. A, always when u do this question move in the opposite direction to the energy travel, u will find that if u moved this way P will move downwards but as Q is maximum it will stay stationary (also for ur information minimum point stays stationary as well)
31.D, R is inversely proportional to d^2 so if u double d u will quarter the resistance at P, but as the question wants in terms of current then it will be 4 at P (as R is incersely proportional to current)[/quote
thanks fr the help bro but cn u explain 25 elaborately

 

[Tkp]

Hela:
for question 7 it might be because at first the total kinetic energy is 1/2 mv^2 and after that we have double the mass which mean kinetic energy is mv^2
as Ek= 1/2mv^2 then mv^2=2Ek then as we have two masses the kinetic energy is spread on both of them so 2Ek/2 will give Ek each and so there is no change in kinetic energy.
NOTE: imnot sure about the way i got the answer, i dont think it is correct.

..m1u1 + m2u2 = ( m1 + m2) v so Y is satationary so u = o so , mu/2m = v so v is 1/2 so the kinetic energy is also halfed so C

 

[littlecloud11]

OH BUddy ur great.nw i got it.ur really genius

Haha, Gracias. Happy to help

 

[Abu mota]

..m1u1 + m2u2 = ( m1 + m2) v so Y is satationary so u = o so , mu/2m = v so v is 1/2 so the kinetic energy is also halfed so C

no actually the answer is A for this question, i check the mark scheme.
anyway for Q.25 direction of energy travel is to the right so you move across the wave in the opposite direction which is to the left, then if u find that your finger goes down when u go across the wave at P, then it will move downwards. i find it very hard to explain how to answer the question, thats the best i can do.

 

[Tkp]

Haha, Gracias. Happy to help

ur frm which country?u have a cute avatar

 

[Tkp]

no actually the answer is A for this question, i check the mark scheme.
anyway for Q.25 direction of energy travel is to the right so you move across the wave in the opposite direction which is to the left, then if u find that your finger goes down when u go across the wave at P, then it will move downwards. i find it very hard to explain how to answer the question, thats the best i can do.

buddy the answer is c.check the markscheme carefully.we;; how the change in kinetic energy would be 0 for an inelastic collison?it should be c

 

[Abu mota]

buddy the answer is c.check the markscheme carefully.we;; how the change in kinetic energy would be 0 for an inelastic collison?it should be c

ok i think i saw a different mark scheme, it all makes sense now i tried to find an explanation for why it is A and i came up with a stupid explanation. ty for pointing it out.

 

[Tkp]

lol

 

[Tkp]

Haha, Gracias. Happy to help

cn u help me to solve mj 06 question 9.i face problems in this type of question.cn u draw it

 

[snowbrood]

cn u help me to solve mj 06 question 9.i face problems in this type of question.cn u draw it

Since it is a velocity - Time graph when the spring is at its lowest and highest position the speed will be equal to zero because it stops for a moment in time to switch direction. The velocity is highest while traveling through the equilibrium position. So the answer will be either b or d.
body first goes up reaches the maximum point and at that point is b and then the body goes down and on reaching minimum point that is D

 

[Tkp]

m nt getting it.i dnt understand these questions.same question in mj07 p1 23.pls cn any1 clear the concept by drawing it?

 

[littlecloud11]

m nt getting it.i dnt understand these questions.same question in mj07 p1 23.pls cn any1 clear the concept by drawing it?

If i drew the Graph it would be same as the one in the question so let me just try explaining using that. You know that when an object is moving through the air it's Kinetic energy will be zero at it's maximum height, right? So naturally, it's velocity will also be zero at maximum height. When am object is at it's equilibrium position the KE is max. hence the speed is also maximum. When you consider the velocity time graph like the one in m/j 06 Find the points where the velocity is zero because they represent the max and min points. The first point (B) shows zero velocity, when you throw an object upwards it reaches it highest point first before it goes down, so B would be the max height. The next point where the velocity is o is D, so that would be the min. height.

For m/j 07 it's a displacement time graph. Again, the same principal applies, at the max and min height the velocity is o. Also, you should know that at the max and min height the acceleration is maximum.This can be proved by the graph below. At point B and D where the velocity is zero the gradient of the curve is actually the steepest, and since the gradient represents acceleration, it's value is max. So your answer to 23 should be D, where the velocity is 0 and acc. max.



Hope this helps!

 

[Tkp]

thnks fr the help.nw its clear

 

[asadalam]

In nov12 p51 q1 they have asked us to vary the speed of the bar magnet as it leaves the coil...is it ok if we explain the use of electromagnets placed above and below the coil and each connected individually to a power supply?