Ken's specialist question thread!

[pi]

^What exactly do you want to do to it?

[b^3]

Assuming you want to solve the differential equation?


Let

[kensan]

^What exactly do you want to do to it?

hahhah yes forgot to mention that 

b^3, yes that's exactly what I wanted, thank you so much

[kensan]

A flexible beam of length D is supported at its ends, which are at the same horizontal level. The deflection y of the beam, measured downwards from the horizontal, satisfies the differential equation where x is horizontal distance from one end.

Find an expression for which I have found to be

Now I need to find an expression for the deflection of y, which I thought would be but according to the answers it isn't, I think I'm failing to pick up some key info from the question that allows me to find c/d, could anyone help me out? cheers

[Mao]

I think your expression is correct.

A flexible beam of length D is supported at its ends, which are at the same horizontal level.

Substitute x=0 and x=D into your final expression, then equate the two:

Without loss of generality, we'll substitute :

And substitute :


As the question states, , so we equate, and arrive at:





The value of d is arbitrary.

[kensan]

I see you have subbed in x=D, and I'm not sure if its a mistype, but is it y=0 or y=d that you have done?

[Mao]

I see you have subbed in x=D, and I'm not sure if its a mistype, but is it y=0 or y=d that you have done?

I updated the previous post with more explanation.

[kensan]

I've got a kinematics question here which I need help with. I'm not very good at these, probably because I don't do physics 
I just need help on how to set this kind of question up, any help appreciated

A particle is projected vertically upwards from the top of a skyscraper with a velocity of 40 m/s and 2 seconds later another particle is projected vertically upwards with a velocity of 25 m/s from the same point. Find
a)   when the two particles meet.
b)   where the two particles meet

[Phy124]

I've got a kinematics question here which I need help with. I'm not very good at these, probably because I don't do physics 
I just need help on how to set this kind of question up, any help appreciated

A particle is projected vertically upwards from the top of a skyscraper with a velocity of 40 m/s and 2 seconds later another particle is projected vertically upwards with a velocity of 25 m/s from the same point. Find
a)   when the two particles meet.
b)   where the two particles meet

Let;
1 = the first ball released
2 = the second ball released





as it is released 2 seconds after, so we have;









Two points meet when





(after the first ball is released)

Then to find the height at which they meet just sub this value into either equation;





*note: (or as written) was taken as with the positive direction denoted as up.

[kensan]

So basically I need to set up simultaneous equations (sort of) when there are 2 objects released at different times.
Awesome thanks so much

[Hutchoo]

So basically I need to set up simultaneous equations (sort of) when there are 2 objects released at different times.
Awesome thanks so much

Yeah, you'll have to do this quite a bit with kinematics and dynamics.
For example, working out when the "police officer catches the criminal" (standard questions) all work on simultaneous equations (with areas).

[Phy124]

So basically I need to set up simultaneous equations (sort of) when there are 2 objects released at different times.
Awesome thanks so much

Yep, you're right on the money there. As Hutchoo pointed out questions like this are pretty standard and revolve all around a good interpretation - the forming of equations and calculations aren't all that hard when you know what you're doing.

Try and do a wide variety of kinematics questions to expose yourself to all the types that VCAA can throw at you, because in my opinion the difficulty of said questions is quite limited and once you grasp that initial understanding you should be fine with most.