Physics help?

rvca

rvca

Member
During World War I, the Germans had a gun

called Big Bertha that was used to shell Paris.

The shell had an initial speed of 2

an initial inclination of 74

The acceleration of gravity is 9

.32 km/s at.5◦ to the horizontal..8 m/s2 .How far away did the shell hit? Answer in

units of km.

if anyone can help me ill be VERY happy

How long was it in the air? Answer in units

of s.

 
speed of 2 what? km/s? m/s?

inclination of 72 degrees?

I feel like their is info missing... that or im reading it wrong.
 
During World War I, the Germans had a gun

called Big Bertha that was used to shell Paris.

The shell had an initial speed of 2

an initial inclination of 74

The acceleration of gravity is 9

.32 km/s at.5◦ to the horizontal..8 m/s2 .How far away did the shell hit? Answer in

units of km.

 
During World War I, the Germans had a gun

called Big Bertha that was used to shell Paris.

The shell had an initial speed of 2

an initial inclination of 74

The acceleration of gravity is 9

.32 km/s at.5◦ to the horizontal..8 m/s2 .How far away did the shell hit? Answer in

units of km.

sorry this should be all the info
 
lnitial speed of 2.32 km/s at inclie of 74.5 degrees

how far away did it hit? units km

how long was it in the air? seconds
 
oh hahah now thats so easy. use the formulas he gave you. i dont remember them that well but ill help you when i have access to my physics book.
 
welp, its projectile motion....

so i know for time spent it is:

time = (2(intial velocity)sin(72))/gravity

and that will give you the time it spends in the air...

so (4sin(72))/9.82 = t

or something to that effect. It looks like he wants to to factor in the earths curvature as well which I don't remember.

As far as the distance traveled, I forgot the physics equation for it, but I know you can do it by creating an equation for the velocity, finding the first derivative to find the speed and then use speed x time = distance.... but thats calculous so there should be an easier way to do it.
 
break it up into x and y

X:

a(t)=0

v(t)=v0x

x(t)=x0+v0*t

Y:

a(t)=-g

v(t)=v0y-g*t

y(t)=y0+v0y*t-(g*t^2)/2

these are your equations now use your knows to solve for time. Use trig to find v0x and v0y, and x0 and y0 are probably zero(i forgot to look at where it started)
 
You have to find t=time first. Then plug it into the distance equation:

Range= Vx(t) where Vx is your intitial horizontal velocity, or the leg of the triangle if you do it that way. Range is simply distance.

Hope that helps, its confusing as fuck at first, but i think i'm starting to grasp it now.
 
i suck, 282.87 km.

fuck it ill write it out.

Vi in the y direction is 2320sin(74.5)=2235.6 m/s (convert km to m)

Vi in the x direction is 2320cos(74.5)= 620 m/s

at the peak of the arch Vf=0 so

Vf=Viy+at

0=2235.6 m/s+(-9.8 m/s^2)(t/2).....t=456.2

for distance:

x=xo+Vixt+1/2gt^2....g=0, xo=0

x= Vix*t= (620 m/s)(456.2 s)=282.87 km

 
edew19 is completely correct..i'm in ap physics now and thats exactly what i'd do to figure it out....

i'd say ++ karma to him
 
figure out the time from the vertical component of bullet velocity

t= speed * sin ø / g

distance is speed * t * cos ø

 
Trick question, the germans didn't know about guns until WW2, they only threw large rocks with their hands and the record distance thrown was 27feet by a man named Valkimuler
 
alright sorry about the joke response, I did a little research becasue I'm at work and bored, and found that I was right about the trick question part, check it:

The Paris Gun of World War I could hurl a 120 kg shell with 7 kg of explosive to a range of 131 km and an altitude of 40 km.

The Paris Gun of World War I (called by the Germans the Kaiser Wilhelm Gun and often incorrectly termed Lange Max or Big Bertha, two completely different guns)

 
I got 28.36km

Vx= 2.32 sin 74.5 = 2.24 km/s

Vy= 2.32 cos 74.5 = .62 km/s

v=vnot + at

0=.62+ -.098t

-.62 = -.098t

t = 6.33s

But because final velocity was 0 (at the top) multiply by two

12.66s

V=X/T

2.24 = X/12.66

2.24*12.66 = X

X = 28.36km

The teacher wanted the answer in km, not meters.
 
you got your Vx and Vy mixed up.

I only converted to meters out of habit. Its way too easy to loose track if you don't use SI units although it would have worked here.
 
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