hard projectile question (1 Viewer)

[bazookie]

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?

 

[Forbidden.]

回复: hard projectile question

http://galileo.phys.virginia.edu/classes/109N/more_stuff/Applets/ProjectileMotion/jarapplet.html

Proof it is 11.7 m/s

Use this equation:

 

[bazookie]

Re: 回复: hard projectile question

how did you get that equation?

 

[Forbidden.]

回复: Re: 回复: hard projectile question

how did you get that equation?

Bear with my notation.

x = v_xt = vcosθ t

y = v_yt + ½at²

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

½gt² = vsinθ t

½gt = vsinθ

t = 2vsinθ / g

Remember

x = v_xt = 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]

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]

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

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

 

[ghost-blade]

Re: 回复: hard projectile question

http://galileo.phys.virginia.edu/classes/109N/more_stuff/Applets/ProjectileMotion/jarapplet.html

Proof it is 11.7 m/s

Use this equation:

i don't get it, if i use that formula then what is the value for theta? do i add the angle of the projectile to 20? if i do that then d will be 8 (for the Q above). PLEASE HELP!

 

[obimoshman1234]

there is no 20 moron learn to read the formula in the brackets is 2 times theta not 20

 

[SH33P]

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

 

[bazookie]

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

 

[SkimDawg]

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.

 

[bazookie]

lol =P

 

[independantz]

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 , but yeah i get your point lol.

 

[bazookie]

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.

 

[Jaspal]

Epic Fail!