Solving Gun Shot Question: Average Horizontal Force Applied to Gun

[madahmad1]

Homework Statement

A rifle is held rigidly by a supporting test frame. When fired horizontallly, a 50 g bullet attains a muzzle exit velocity of 500 m/s if it takes 0.003 s for the bullet to travel the length of the barrel, determine the average horizontal force applied to the gun by the test frame during firing.

Homework Equations

The Attempt at a Solution

I know that the answer is 8.33 kN but I do not know how to solve it.
I think that we evaluate the forces on the x axis, there are no forces on the y-axis but
i am not sure, any help?

 

[tiny-tim]

I know that the answer is 8.33 kN

Hint: 8330 is half of 50/.003.

 

[madahmad1]

lol, so i multiply 50/0.3 by a half? Thanks for the help but can you tell me what steps i should take, i really do not get this problem.

 

[BryanP]

F = ma

With what you're given, how can you find the acceleration?

You have the mass, but you have to change it's units so you can get the force in Newtons (N).

 

[tiny-tim]

(i must admit i think it's a badly-worded question, and i don't really understand the mechanical set-up … but what they obviously want is …)

ok … Newton's second law …

force = mass times acceleration​

so …

average force = mass times average acceleration …​

and average acceleration is … ?

 

[madahmad1]

In order to find the average force we need to know the average acceleration,to find the average acceleration we divide 500/0.003, which is velocity divided by time. This comes out to be 166666.667., then we multuply by 50, correct? I`m sorry if i am wrong but I am really trying to answer this based on the help you are giving me, do we find average acceleration by a different method?

 

[tiny-tim]

In order to find the average force we need to know the average acceleration,to find the average acceleration we divide 500/0.003, which is velocity divided by time. This comes out to be 166666.667., then we multuply by 50, correct?

No … 1 N = 1 kg m /s² … so we multiply by 0.05.