Calculating Projectile Acceleration and Barrel Travel Time

• ataglance05
In summary, the battle ship fires three rounds from its foward turret at an angle of 10 degrees above the horizontal. Each projectile weighs 1220 kg, and has a muzzle velocity of 770 m/sec. The acceleration of each projectile in the barrel is negative, and it takes .0543 seconds for the projectiles to travel down the barrel.
ataglance05

Homework Statement

A battle ship (4.09*107 kg) fires a salvo of 3 rounds from its foward turret in the direction of the bow at an angle of 10 degrees above the horizontal. Each projectile weighs 1220 kg, each barrel is 20.9 m long and the muzzle velocity (I don't know whether this is initial or final velocity) of the projectile is 770 m/sec.

What is the acceleration of each projectile in the barrel and how long does it take to travel down the barrel?

Homework Equations

Vf=Vi + a(T)
S= Vi(T) + 1/2(a)(T)^2
a= vf-vi/T

The Attempt at a Solution

no clue!

Last edited:
I would assume that the muzzle speed is that of the projectile at the end of the barrel.

robb_ said:
I would assume that the muzzle speed is that of the projectile at the end of the barrel.

projectile starts with a speed of 770 m/sec.

You want to determine the acceleration of the projectile while in the muzzle, right? It seems the only reasonable thing to assume is that the projectile attains the "muzzle speed" at the end of the muzzle, at least to me.

*edit* and yes they are sweet.

Last edited:
Here's what I've concocted so far. However, I'm not sure if it's correct, for the acceleration comes out to be negative and i don' think i could get a negative acceleration for this type of problem:

a=(vf-vi)/t
a= -770/t

a= -770/.0543
a= -14180 m/sec^2

S=Vi(T) + 1/2(a)(T)^2
20.9=770(T) + 1/2 (-770/T)(T)^2
20.9=770(T) - 385(T)
20.9=385(T)
T=.0543 sec

To me it looks like you are stating that the initial speed is 770 and the final speed is 0. That doesn't make sense to me.

robb_ said:
To me it looks like you are stating that the initial speed is 770 and the final speed is 0. That doesn't make sense to me.

so would it be the other way around?? initial velocity is 0 and final velocity is 770??

a=(vf-vo)/t
a=770/t

a=770/.018= 42777 m/sec^2

S= Vo(T) + 1/2(A)(T)^2
20.9=770(T) + 1/2 (770/T)(T)^2
20.9= 1155(T)
T= .018 sec

??

This is right, but perhaps a more straightforward approach assumes vf=770, and Vi=0,

Given that Vf^2-Vi^2=2ax, then a=770^2/(2*20.9)
a=14184m/s^2 and t would just be the distance divided by ave velocity:
20.9/385=0.0543s Different ways to skin a cat. Best to have many knives.

Yes the solution is the same mathematically, but physically, at this level, hmmmm?
If the OP recognizes that both problems are the "same," then great!

me and denverdoc contrived totally different answers. So which one would be right? I'm not sure if my calculations from my previous post were valid anyway.

Oh, sorry didnt catch your last post. You now should consider the initial speed of the projectile in your distance equation.

robb_ said:
Oh, sorry didnt catch your last post. You now should consider the initial speed of the projectile in your distance equation.

HA! I got it! thank you both, robb_ and denverdoc.

cheers.
: )

What are projectiles?

Projectiles are objects that are launched or thrown, and follow a curved path due to the force of gravity acting on them. Examples of projectiles include arrows, bullets, and balls thrown in sports.

What is the difference between a projectile and a non-projectile?

The main difference between a projectile and a non-projectile is the presence of a curved path. Non-projectiles typically follow a straight path, while projectiles are affected by the force of gravity and follow a curved path.

What factors affect the trajectory of a projectile?

The trajectory of a projectile is affected by several factors, including the initial velocity, the angle of launch, air resistance, and the force of gravity. These factors determine the height, distance, and shape of the projectile's path.

Can a projectile change its trajectory?

Yes, a projectile's trajectory can be changed by altering any of the factors that affect it. For example, changing the initial velocity or angle of launch can result in a different trajectory. Additionally, external forces such as wind or air resistance can also impact the trajectory.

How are projectiles used in real life?

Projectiles have many practical applications in everyday life, including in sports, military operations, and transportation. They are also used in scientific experiments and studies to understand the laws of motion and gravity.

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