Question

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 0.765 km/s at an initial inclination of 36.2◦ to the horizontal.
The acceleration of gravity is 9.8 m/s^2.
How far away did the shell hit?
Answer in units of km

Answer 1

Are you familiar with the range equation? \[\huge R = \frac{ v_o ^2 \sin (2 \theta) }{ g }\] if so you can use it here.

If not you'll have to start by breaking the velocity up into horiz and vertical components.

Answer 2

I don't understand this problem at all. ):

Answer 3

I'm not familiar with the range equation either...

Answer 4

Start by finding the components of v then
use sine and cosine to find Vx and Vy.

Answer 5

I got 569.22 but it's not right.

Answer 6

I mean I got 569.22 for the final answer...

Answer 7

Well idk what the final answer is, but i can work it out with the range equation... but for now just work out Vx and Vy

Answer 8

I put V in m/s just to be safe, we can get km/s back later

Answer 9

So Vy is 451.81 and Vx is 617.32?

Answer 10

Very good :D Now, find the time taken, using Vy. When the object hits the ground, Vy will be equal but in the opposite direction... ie -451.81

So use the equation \[\Large v_f = v_i + a t\]
where vi is 451.81, vf is -451.81, and a=-9.8m/s^2 (negative since it's in the same direction as the downward v)... find t.

Answer 11

Once you have t, just use distance = Vx*time

btw it looks like your answer was only off by a factor of 10... 569.22 when it should be more like 56.92 km.

Answer 12

Oh yeah... it is 56.92! I can't believe I messed up at the easiest part of the problem haha. ^-^ thanks.

Answer 13

haha i figured i'd check and thought you'd just forgotten to divide by g somewhere! :)

Answer 14

Well I got a 98% on my homework so I'm pretty happy. (:

Answer 15

aw yay! :D