Physics CRAMMM!!! (1 Viewer)

[FinalFantasy]

Cram Cram Cram!!
I'm sooo screwed LoL!
Gota cram it all in before tomorrooowwwwwwwww!!

 

[lum]

cramming till 4 for me same for chem, lol

 

[physician]

wohooooo a cramming thread

till 4.....???

instead of staying until 4 .. i will probably sleep at 1 and wake up at 5:30

study from 6-11

exam at 12

ahhhhh...

i still have major cramming... ahhhhh

i hope it's as easy as last yrs paper.... they asked all the easy stuff... not fair!!!

i hope MM isn't in the exam....

 

[scoby_2000]

why am i here?! i should be in my room studying!?

wait...im waiting for answers

(procrastination is justified )

 

[Jago]

somebody scan the exam after you're done, i need practice for my trials (not doing cssa, dont worry)

 

[FinalFantasy]

^scoby y don't u post any questions u are unsure of and we can discuss and thus learn a thing or two

 

[scoby_2000]

ok

Usinmg the data in the table below answer the following question.

(Table)
Planet - Acc. of Gravity
Earth - 9.8ms^2
Mars - 3.7ms^2

a person stood on scales that were designed for the Earth whilst on Mars. The scale gave a reading of 50kg. What is the actual mass of the person?

A) 132.4kg
B) 50kg
C) 18.9kg
D) 490 N

(i know this is an easy question but its just im a simple person you see!)

and this one

A projectile is fired horizontally at 10ms^-1 from the top of a cliff, 55m high, into the water. What is themagnitude of its velocity as it impacts with the water?

A) 32.8ms
B)1078ms
C) 1175.8ms
D) 34.3ms

could any one please give answer and an explanation?

ps...i am dumb

 

[FinalFantasy]

ok the first q.
a person stood on scales that were designed for the Earth whilst on Mars. The scale gave a reading of 50kg. What is the actual mass of the person?

A) 132.4kg
B) 50kg
C) 18.9kg
D) 490 N

first of all it's not D cuz it asks for "mass", and since the scale gave reading of 50kg while on Mars, on Earth it should give a bigger reading so B is also wrong and so is C, so A is da only choice

Edit: Note u can also do this question using the equation w=mg, but i prefer to do it this way cuz im lazy to type things in calculator

 

[scoby_2000]

i think A) because 1. its the only answer i get from a calc. and 2.

this looks rite

50 / 37 = 13.5

13.5 x 9.8 = 132.4

y i use that calculation i know not....but it comes out with A) so

 

[Dumsum]

The good thing about physics in comparison to chemistry is that the course has about half as much content... so cramming seems much more viable.

I have my exam tommorow too. I hope it's the CSSA, I like their science exams. (teachers at our school kinda switch around between catholic, independant etc)

 

[FinalFantasy]

A projectile is fired horizontally at 10ms^-1 from the top of a cliff, 55m high, into the water. What is themagnitude of its velocity as it impacts with the water?

A) 32.8ms
B)1078ms
C) 1175.8ms
D) 34.3ms

using v²=u²+2as
v²=100-2*9.8*-55
by calculator v=34.3
so D??
im inefficient with this physics stuff so excuse me if im wrong

 

[physician]

A projectile is fired horizontally at 10ms^-1 from the top of a cliff, 55m high, into the water. What is themagnitude of its velocity as it impacts with the water?

A) 32.8ms
B)1078ms
C) 1175.8ms
D) 34.3ms

using v²=u²+2as
v²=100-2*9.8*-55
by calculator v=34.3
so D??
im inefficient with this physics stuff so excuse me if im wrong

100?.. initial vertical is equal to zero since it is fired horizontally

look at my solution in the other thread... although i think u did get the correct answer

 

[FinalFantasy]

i used the initial horizontal instead of vertical...
think it gives direct velocity of impact...
but i dunno, as i said im inefficient w\ these hahaha

 

[physician]

i used the initial horizontal instead of vertical...
think it gives direct velocity of impact...
but i dunno, as i said im inefficient w\ these hahaha

but in projectile calculaions.. gravity is not acting on the horizontal velocity.. it only effects the vertical... as galileo proposed that they motion of projectiles could be seperated into two components...

although this is not completely true in reality.. but experimental evidence can show that his assumption is almost accurate... (keeping in mind that whilst we calculate the vertical cmponent we are neglecting air resistance)

so i don't see how u can use horizointal velocities with gravity....

but once again... i think ur answer is correct... the other two are completely wrong

it's eothet A or D

i'm thinking the later.. as i caluculated the vertical final velocity to be A

 

[FinalFantasy]

A projectile is fired horizontally at 10ms^-1 from the top of a cliff, 55m high, into the water. What is themagnitude of its velocity as it impacts with the water?

A) 32.8ms
B)1078ms
C) 1175.8ms
D) 34.3ms

y''=-10
y'=-10t+C, at t=0, y'=0, .: c=0
.: y'=-10t
y=-5t²+C
at t=0, y=55 , .: C=55
.: y=-5t²+55

now, at y=0
5t²=55
t²=11
t=root 11
at t=root 11, y'=-10 root 11=-33.17

so as it impacts the water, the velocity²=(-33.17)²+10²=34.6 m\s

lol
so i guess it's D

 

[Dumsum]

A projectile is fired horizontally at 10ms^-1 from the top of a cliff, 55m high, into the water. What is themagnitude of its velocity as it impacts with the water?

A) 32.8ms
B)1078ms
C) 1175.8ms
D) 34.3ms

y''=-10
y'=-10t+C, at t=0, y'=0, .: c=0
.: y'=-10t
y=-5t²+C
at t=0, y=55 , .: C=55
.: y=-5t²+55

now, at y=0
5t²=55
t²=11
t=root 11
at t=root 11, y'=-10 root 11=-33.17

so as it impacts the water, the velocity²=(-33.17)²+10²=34.6 m\s

lol
so i guess it's D

You'd probably get on the answer if you used 9.8.

Now I must ask this question: Can we use this method in physics?? Because in all honesty it's just so much clearer. I know we're not allowed to use the formulae in maths, but what about using the integration in physics?

 

[FinalFantasy]

yea i took g=-10 instead of 9.8 which the question wants
i not sure about maths in physics, but physics in maths u surely can't
o well im gonna do dis to check answers anyway lol

 

[helper]

Yes, you can use the maths method in physics. You can also use valid equations not in the syllabus.

 

[FinalFantasy]

^ wow that's awesome!
well im gonna try it out in the trials tomorrow and c wat happens
if i get full marks den i'll do it in da HSC as well

 

[physician]

yeh it is D 100%


all u have to do is the folliwng:

v² = u² + 2as

a = 9.8 m/s²

s= 55 m

u (initialy vertical) is equal to 0

therefore v² = 0 + 2(9.8)(55)

v= 32.8 (1 dec. place)

but v is the vertical final velocity
the intial horizontal is qual to the final horizontal therefore final horizontal = 10m/s

10² + 32.8² = final velocity sqaured

final velocity is equal to

... 34.3 m/s

which is D