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hard projectile question (1 Viewer)

bazookie

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a long jumper left the ground at an angle of 15 degrees and jumped a distance of 7m. Considering this result, calculate the velocity of the long jumper when leaving the ground.

answer is 11.7

how the fuck?
 

bazookie

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Re: 回复: hard projectile question

how did you get that equation?
 

Forbidden.

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回复: Re: 回复: hard projectile question

bazookie said:
how did you get that equation?
Bear with my notation.

x = vxt = vcosθ t

y = vyt + ½at2

0 = vyt - ½gt2 (Final y-coordinate of projectile is 0 i.e. the ground)

½gt2 = vsinθ t

½gt = vsinθ

t = 2vsinθ / g

Remember

x = vxt = vcosθ t = (vcosθ) (2vsinθ / g) = 2v2sinθcosθ / g

(sin2θ = 2sinθcosθ)

x = v2sin2θ / g

(d = x yada yada ....)

In HSC Physics you don't need to know the proof
 

philxe

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Re: 回复: Re: 回复: hard projectile question

you can use the maths formulae but is it true that they will only award 1 mark for the answer since the working isn't following the physics formulaes.

Anyway, you solve this prove by using the horizontal equation and vertical equation.

using 7 = V cos 15 x T, you derive an equation for T

then substituting T in to 0 = V sin 15 x T - 4.9 T^2

and you should come up with V^2 = 240.1 / 7 tan 15 x cos^2 15

taking the positive square root giving you 11.7 approx
 

jussybussy

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Re: 回复: Re: 回复: hard projectile question

philxe said:
you can use the maths formulae but is it true that they will only award 1 mark for the answer since the working isn't following the physics formulaes.

Anyway, you solve this prove by using the horizontal equation and vertical equation.

using 7 = V cos 15 x T, you derive an equation for T

then substituting T in to 0 = V sin 15 x T - 4.9 T^2

and you should come up with V^2 = 240.1 / 7 tan 15 x cos^2 15

taking the positive square root giving you 11.7 approx

u will get full marks if u get the right answer.... if u get the wrong answer however, zero marks as opposed to instead of using the 3unit formulas, using the physics formulas and having correct working but the wrong answer where u could possibly still get full marks
 

SH33P

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bazookie said:
a long jumper left the ground at an angle of 15 degrees and jumped a distance of 7m. Considering this result, calculate the velocity of the long jumper when leaving the ground.

answer is 11.7

how the fuck?
maths is over... dont pollute BOS with useless CRAP :p
 

bazookie

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yea this is physics, fuckstick. How is it useless crap when i'll be needing this in two days?

GTFO, stop polluting bos with YOUR useless crap.

edit: fuck you kthnxbye
 
Last edited:

SkimDawg

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bazookie said:
yea this is physics, fuckstick. How is it useless crap when i'll be needing this in two days?

GTFO, stop polluting bos with YOUR useless crap.

edit: fuck you kthnxbye
Such violence, I suggest go for a paddleboat ride.
 

independantz

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bazookie said:
yea this is physics, fuckstick. How is it useless crap when i'll be needing this in two days?

GTFO, stop polluting bos with YOUR useless crap.

edit: fuck you kthnxbye
Actually, theoretically it's maths :p, but yeah i get your point lol.
 

bazookie

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i know it's maths but he's saying maths is over so i should stop talking about it...

so i said this is physics. physics requires maths. Just because maths the subject is finished doesn't mean it's useless in other subjects.
 

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