Projectile Help! (1 Viewer)

[zxreth]

Hey guys i need help with the following projectile questions, i've done part i) for both of them but cant manage to make any progress on the rest, any help would be appreciated!
Thanks =]

Link 1: http://i56.tinypic.com/ofaa7l.jpg
Link 2: http://i53.tinypic.com/rsyk5k.png

 

[tambam]

Okay, for the first question:
ii)
- Sub p=x into x=vtcosa
- Rearrange to make t the subject (Equation 1)
- Sub h=y into y= -5t^2vtsina (Equation 2)
- Sub the value of t for Equation 1 into Equation 2
Then if you play around with it, it will come up with the answer (but tell me if you need a better explanation) - You need to remember that 1+tan^2a=sec^2a

ii)
From the result for part i), sub in the q for p, so you have 2 equations with V^2 as the subject.
Then you can put the two together, because they both equal to V^2
Then play around with it to get your answer.

Hope that helps, tell me if anything needs clarifying, or you need more detail

 

[tambam]

Second question:
ii)
- For the plane, x'=U (horizontal velocity)
- Integrating gives x= Ut + AB (Because at t=0, the shell is at position B) - Equation 1
- Construct a right-angle triangle, with angle alpha, height h .
- tan(alpha) will give you h/AB, rearrange to get AB= h/tan(alpha)
- sub this value of AB into Equation 1
- You then get x= Ut+ h/tana, replace x with Vtcosa to give you the answer
iii)
- Sub h into the equation of y Equation 2
- From the answer in part ii), rearrange to make T the subject
- Sub T into Equation 2
- Play around with it until you get the answer

 

[Drongoski]

Okay, for the first question:
ii)
- Sub p=x into x=vtcosa
- Rearrange to make t the subject (Equation 1)
- Sub h=y into y= -5t^2vtsina (Equation 2)
- Sub the value of t for Equation 1 into Equation 2
Then if you play around with it, it will come up with the answer (but tell me if you need a better explanation) - You need to remember that 1+tan^2a=sec^2a

ii)
From the result for part i), sub in the q for p, so you have 2 equations with V^2 as the subject.
Then you can put the two together, because they both equal to V^2
Then play around with it to get your answer.

Hope that helps, tell me if anything needs clarifying, or you need more detail

That's correct. But zxreth may like the full workout - always so tedious!

 

[Drongoski]

For Q1

i)














By the same but less tedious process:




ii)


Now say projectile passes thru the 2 points P(p,h) and Q(q,h) at t = T₁ and T₂ resp.







iii)

Similarly:

The 2 expressions for V² being equal:

 

[tambam]

Yeah, its too much effort to put all the working
And generally with questions like that, if you get a clue to the next step, you can normally work it out.

(Also, how do you make the equations look like that, is it some complicated html stuff)

 

[Drongoski]

No. I just use TeX (or LaTeX)

 

[zxreth]

For Q1

i)














By the same but less tedious process:




ii)


Now say projectile passes thru the 2 points P(p,h) and Q(q,h) at t = T₁ and T₂ resp.







iii)

Similarly:

The 2 expressions for V² being equal:

thanks drongoski, you make it look so easy