projectile question (2 Viewers)

[sub]

glad to have made ur day...it was my best exam of the hsc...glad to leave on a high note

 

[mozzie]

220.9 wasnt it

 

[lucyinthehole]

yep got 220.8 for the range

got the mass of the moon wrong, i don't know why, but i did everything right in the next part, hoping they'll treat it as carryover mistake.

 

[fush]

yea dont worry, my answer might not be right, i think it was that though

 

[gerardk]

dammit!! im pretty sure i got the rang to be 120m or summin. arghh..anyone else get this and know why they were wrong??

 

[fush]

im pretty sure i was right....i found the time of flight by using
delta y = Uy t + 1/2 a t squared
then u let delta y = o for time of flight...
then u use the time which was round 5.1 seconds if i remember, and the u sedi t in the delta x = Ux t

which gave u round 220 delta x = 50cos30 . 5.1
= 220 m

 

[bevstarrunner]

yeah yeah...just the horizontal velocity x hang time eh..??

 

[fush]

yea sorry...

range = horz. velocity times time of flight
= 50cos30 times 5.1
= round 220m

 

[DI2AGON]

there's an actual equation that u could of just used straight away

R = u^2 sin20 / g

where u = initial velocity
0 = theta which was 30 and g = 9.8

omg for a 4 mark question it saved so much time

answer was 220.9

 

[fush]

yea from 3u maths..but i forgot it and i couldnt be bothred working it out

 

[BillyMak]

Not sure you would get 4 marks for that....
You used an equation that wasn't in the syllabus, and if a marker saw that I doubt that they would say that you did all of the working required.

But then again, I'm not a marker.

 

[DI2AGON]

i dont see why u wouldn't, and besides i actually got that from the success one book for physics, and i'm pretty sure if u get the answer right u get full marks

 

[gordo]

i just did velocity = distance / time
distance = 2.pi.r
time = 7000 odd seconds

then u end up with the velocity

 

[fush]

for waht question gordo?

 

[Willmaker]

yea from 3u maths..but i forgot it and i couldnt be bothred working it out

Both my 2u/3u maths teacher and physics teacher said NOT to use physics formulae in maths and NOT to use maths formulae in physics.

 

[maniche]

it was 220.9 m
because R (range) equals usquared times 2sin over g

 

[Komaticom]

1. find vertical initial velocity
2. find time to max height
3. 2x time to max height
4. find horizontal initial velocity
5. 2x time to max height x horizontal intial velocity

I think that's the simplest method... not sure though.

 

[johnlindsay1]

best formulae for range = (u squared times by sin 2theta) divided by g. got range in abut 2 secs. worked out to be 221m.

 

[A2RAYA]

1600 something like that for the velocity

yeh 1628 m/s for that

221m for range and 7.35x10^35 kg for mass

i might do good in a physics exam for once

 

[Komaticom]

Using maths formulae to solve physics questions. Damn you all! This is physics, use the formulae they want you to use. They might not understand your maths range formula, bahaha.