Projectile Question (Not making any sense)

[kozis]

Hello guys..I am new in the forum,glad to find you and I think a great work is done here.So my problem is that I have a question on projectiles,I've solved easily the first part but the second part doesn't make any sense to me.I don't even know what it means.Note that english is not my first language.So the problem:

Homework Statement

A gun which is situated precisely at the North Pole fires a shell at an angle of inclination of 60 deg.the horizontal.The initial speed of the shell is 600 m/s.It can be assumed that the terrain is flat and that air resistance can be neglected.
a)How far from the gun will the shell land?

b)If the gun was aimed at a target without taking into account the rotation of the Earth,how far off target would the shell be?

The Attempt at a Solution

As I've told you i solved the first part but part b) doesn't make any sense to me! If anyone can explain what it means please! "without taking into account the rotation of the earth?" was it taken into account before? I'm so confused:p
Thank you!

 

[Doc Al]

You didn't need to take the rotation of the Earth into account for part a, since it only asked about the distance. Hint for part b: The target moves with the earth. How far does it move during the flight of the shell?

 

[kozis]

Don't I need the radius of earth?

 

[Doc Al]

Don't I need the radius of earth?

No, but you'll need the angular velocity of the earth. Figure that out.

 

[kozis]

Here's what I did..I found the angular velocity of Earth by doing ω=2π/86400 and then I found the angle by θ=ωt. Then using a triangle I did tanθ= distance target moved/range. But the result I'm getting is way out of that i should get. I find 4,27m and the answer should be 245m..I can't figure out what I am doing wrong.

 

[gneill]

What values did you get for range, time, and angle θ ?

 

[kozis]

So, for range is what I've found in a) which is 31800m and correct according to the answers. t=106 s and θ=7.7x10^-3

 

[gneill]

So, for range is what I've found in a) which is 31800m and correct according to the answers. t=106 s and θ=7.7x10^-3

Okay, those values look all right to me. You should be finding the correct target offset with these values. Check the calculation again, and if it's still not giving you the right answer, post the details step by step.

 

[kozis]

I have attached an image of extaclty what i did. I hope am not doing any stupid mistake:p

 

[kozis]

Ok I've found it! Angle is in radians,my calculator was set up in degrees. Thank you both !