hey, for question 3d why do we use v=-Awsinwt and not v=Awcoswt? i thought that because she swings from end A that would be starting at the max and so would be the cos function? terrific videos btw :-)
Thanks Tree Stump! For starting at the maximum we use the cos function for the displacement (y=Acosθ), but the sin function for the velocity (v=Aωsinθ). Hope that helps.
Cheers Daniel! The angle that the plane is banked by is the angle between the lift force and the vertical axis (the gravitational force points downwards along this axis).
@@Asher137 Hi Ash, good question. You're correct that Fc would be between the two forces however, Fc is not a force itself, it's a role that other forces play. In this case it is provided by the horizontal component of the lift force. To better imagine where to put the 35° angle, I suggest drawing the forces for a plane that isn't banked. In this case the angle of banking is zero, as is the angle between the lift and gravitational force (they will point opposite to each other). As you increase the banking angle, notice that the angle between the lift and gravitational force will increase by the same amount, because these angles are the same. Hope that helps!
@@MrWhibleyPhysics This is life changing information!!! Thank you so much Mr Whibley 🙏🙏🙏 😭you are the only reason I got Excellence on my formatives... Thank you so so much for replying
Cheers Liam! θ is the total angle rotated through. The total angle between A and B is π (180°). From our point in question the angle to B is φ. This means that the total angle θ is equal to π - φ. Hope that helps.
Hi NinjaPirate, one set of equations is for the system starting at y=0 and the other y=A. See my note video here: ruclips.net/video/BYjNjme4LtQ/видео.html
Hi Ninja Pirate. Correct, the banked example is depicted in the second picture. When the plane is banked the lift force is no longer entirely vertical, part of it now points horizontally. This is what we're calling the horizontal lift component. It is what is providing the centripetal force causing the plane to move in a circle. Hope that helps!
In question 3c would this be correct if I said this: The acceleration is proportional to the displacement from the equilibrium position, and The acceleration acts towards the equillibrium position? Would this way be correct or do I have to talk about the restoring force?
Great question. While your statement is correct, the graph is of specifically the restoring force and the assessment schedule is worded only in terms of the restoring force. For that reason I'm not 100% sure the markers would give you the full mark for only talking in terms of the acceleration.
@@MrWhibleyPhysics Is it fine if I swapped the acceleration and write it with the restoring force? Can I also replace the word proportional to the opposite direction?
Because she stands and shifts her mass upwards, her centre of mass moves upwards. The length of a pendulum is specifically defined as being from the pivot to centre of mass, so by definition it has shortened.
The radius is the distance between the plane centre and the earth centre. To find this distance we need to add the distance between the earth centre and the earth surface to the distance between the earth surface and the plane centre.
Not quite as sin and cos are pi/2 apart, not pi. To use cos you would need to subtract pi/2 from the angle like this www.wolframalpha.com/input?i=-1.5*1.8cos%28pi-0.841-pi%2F2%29
In question 2a, are you supposed to square the radius.
Good catch Peseti, it is meant to be 0.2^2. Seems I remembered to square it on the calculator however, so the numbers are otherwise correct.
hey, for question 3d why do we use v=-Awsinwt and not v=Awcoswt? i thought that because she swings from end A that would be starting at the max and so would be the cos function? terrific videos btw :-)
Thanks Tree Stump! For starting at the maximum we use the cos function for the displacement (y=Acosθ), but the sin function for the velocity (v=Aωsinθ). Hope that helps.
Hey Mr. Whibley, huge fan. Whats the best way to figure out where to put our angle in question 1c?
Cheers Daniel! The angle that the plane is banked by is the angle between the lift force and the vertical axis (the gravitational force points downwards along this axis).
@@MrWhibleyPhysicsHi! Sorry I don’t understand :( wouldnt Fc be between the two forces? How did you know it went between Fg and Fl
@@Asher137 Hi Ash, good question. You're correct that Fc would be between the two forces however, Fc is not a force itself, it's a role that other forces play. In this case it is provided by the horizontal component of the lift force.
To better imagine where to put the 35° angle, I suggest drawing the forces for a plane that isn't banked. In this case the angle of banking is zero, as is the angle between the lift and gravitational force (they will point opposite to each other). As you increase the banking angle, notice that the angle between the lift and gravitational force will increase by the same amount, because these angles are the same. Hope that helps!
@@MrWhibleyPhysics This is life changing information!!! Thank you so much Mr Whibley 🙏🙏🙏 😭you are the only reason I got Excellence on my formatives... Thank you so so much for replying
@@Asher137 Cheers Asher! Congratulations on getting Excellence on your formatives. You should be well on track for the Final in November. Good luck!
hey mate, your videos are really helpful. in Q3d, why did you do v= awsin(pi - 0.841), rather than v =awsin(0.841)?
Cheers Liam!
θ is the total angle rotated through.
The total angle between A and B is π (180°).
From our point in question the angle to B is φ.
This means that the total angle θ is equal to π - φ.
Hope that helps.
For reference circles, whats the difference between V=Aωcosθ and
V=-Aωsinθ and how do I know which one I'm suppose to use?
Hi NinjaPirate, one set of equations is for the system starting at y=0 and the other y=A. See my note video here: ruclips.net/video/BYjNjme4LtQ/видео.html
For question 1b, is the banked example the second picture? Also what is a horizontal life component in a centripetal force?
Hi Ninja Pirate. Correct, the banked example is depicted in the second picture.
When the plane is banked the lift force is no longer entirely vertical, part of it now points horizontally. This is what we're calling the horizontal lift component. It is what is providing the centripetal force causing the plane to move in a circle. Hope that helps!
@@MrWhibleyPhysics Oh thanks
In question 3c would this be correct if I said this: The acceleration is proportional to the displacement from the equilibrium position, and The acceleration acts towards the equillibrium position? Would this way be correct or do I have to talk about the restoring force?
Great question. While your statement is correct, the graph is of specifically the restoring force and the assessment schedule is worded only in terms of the restoring force.
For that reason I'm not 100% sure the markers would give you the full mark for only talking in terms of the acceleration.
@@MrWhibleyPhysics Is it fine if I swapped the acceleration and write it with the restoring force? Can I also replace the word proportional to the opposite direction?
In question 3b when Selena stands up where is her COM? Also how does the COM reduce the length of the pendulum?
Because she stands and shifts her mass upwards, her centre of mass moves upwards. The length of a pendulum is specifically defined as being from the pivot to centre of mass, so by definition it has shortened.
@@MrWhibleyPhysics thank you very much
For question 3d why didn't you use the equation y=Acoswt did you use it as a guide?
Hi Ananomous Rex, I mentioned y=Acoswt only as a lead into explaining my choice of v=-Awsinwt.
For question 1d, why did you add 1.28x10^4 with 6.37x10^6 as the radius
The radius is the distance between the plane centre and the earth centre.
To find this distance we need to add the distance between the earth centre and the earth surface to the distance between the earth surface and the plane centre.
@@MrWhibleyPhysics Oh I see, thanks
For the last question, will I still get the same answer -2.01ms^-1 if I used V=Aωcosθ
Not quite as sin and cos are pi/2 apart, not pi. To use cos you would need to subtract pi/2 from the angle like this www.wolframalpha.com/input?i=-1.5*1.8cos%28pi-0.841-pi%2F2%29
Thanks a lot!! :)
Hello is the damping effect a question in ncea level 3 mechanics systems?
It does occasionally come up. See 3c of the 2019 Mechanical Systems exam.
Just did the physics exams, and Sir I am not capping, the mechanics paper is tough as hell.
If that's the case hopefully the marking schedule is forgiving! I'll sit down with the papers this weekend and try them myself.
@@MrWhibleyPhysics I hope so too, may ncea go easy on us
@@JB-et8re lol did it?
thank you!!!1