Discussion about math, puzzles, games and fun. Useful symbols: ÷ × ½ √ ∞ ≠ ≤ ≥ ≈ ⇒ ± ∈ Δ θ ∴ ∑ ∫ π -¹ ² ³ °

You are not logged in.

- Topics: Active | Unanswered

Pages: **1**

**luca-deltodesco****Member**- Registered: 2006-05-05
- Posts: 1,470

ive started Mech 2 as an additional module that i don't actually need, but i want to do anyways, but im having trouble with one of the questions on projectiles.

Basicly, a projectile is fired with initial speed u = √ag where a is a constant, and g is acceleration due to gravity, at angle θ.

it is fired off of a cliff of height b metres.

the first part is to show that:

i did this ok, and then the next part is this:

Show that the maximum value of x (i.e. the value of x when it hits ground at bottom of cliff) as θ varies is

.i also did this fine after a bit of thought, however i can't quite get the last part.

Show that this is achieved when

this is where i get stuck, anyone help?

*Last edited by luca-deltodesco (2007-03-20 05:58:10)*

The Beginning Of All Things To End.

The End Of All Things To Come.

Offline

**luca-deltodesco****Member**- Registered: 2006-05-05
- Posts: 1,470

The Beginning Of All Things To End.

The End Of All Things To Come.

Offline

**luca-deltodesco****Member**- Registered: 2006-05-05
- Posts: 1,470

ah wait, i figured it out, i was trying to solve this by simply plugging the value of x = √a(a+2b) into the equation, but it got very messy.

but i remember, if the discriminant is 0, i.e. x IS √a(a+2b) then the value of ax^2 + bx + c = 0, is -b/2a

i.e.

The Beginning Of All Things To End.

The End Of All Things To Come.

Offline

**Stanley_Marsh****Member**- Registered: 2006-12-13
- Posts: 345

what is x anyway?

Numbers are the essence of the Universe

Offline

**luca-deltodesco****Member**- Registered: 2006-05-05
- Posts: 1,470

x and y are just the x and y displacements

The Beginning Of All Things To End.

The End Of All Things To Come.

Offline

**JaneFairfax****Member**- Registered: 2007-02-23
- Posts: 6,868

*Last edited by JaneFairfax (2007-03-20 10:06:26)*

Offline

**luca-deltodesco****Member**- Registered: 2006-05-05
- Posts: 1,470

a different way of doing it, but with same results

The Beginning Of All Things To End.

The End Of All Things To Come.

Offline

Pages: **1**