Force of nail after being struck by a hammer

[unteng10]

Homework Statement

A 5lb hammerhead, traveling at 5.4ft/s strikes a nail and is brought to a stop in .00081s. The acceleration of gravity is 32ft/s^2, What force did the nail recieve?

Homework Equations

The equation I have is F=Pf-Pi/delta T. Both Pf and Pi have a arrow above them going to the right.

The Attempt at a Solution

I know I have to find Pf and Pi, and P=mv. With that said would Pf be 0, since it comes to a stop, and Pi be (5lb)(5.4ft/s)? And I am guessing that delta T would .00081s?

 

[LowlyPion]

Homework Statement

A 5lb hammerhead, traveling at 5.4ft/s strikes a nail and is brought to a stop in .00081s. The acceleration of gravity is 32ft/s^2, What force did the nail recieve?

Homework Equations

The equation I have is F=Pf-Pi/delta T. Both Pf and Pi have a arrow above them going to the right.

The Attempt at a Solution

I know I have to find Pf and Pi, and P=mv. With that said would Pf be 0, since it comes to a stop, and Pi be (5lb)(5.4ft/s)? And I am guessing that delta T would .00081s?

Welcome to PF.

The real question here is what is the mass of the hammerhead? Since they give you acceleration of 32ft/s², then this suggests to me this is how much it weighs. So I would say you need to determine your mass as 5/32 and then multiply by your 5.4 to get your momentum and then proceed as you were apparently intending.

 

[unteng10]

Welcome to PF.

The real question here is what is the mass of the hammerhead? Since they give you acceleration of 32ft/s², then this suggests to me this is how much it weighs. So I would say you need to determine your mass as 5/32 and then multiply by your 5.4 to get your momentum and then proceed as you were apparently intending.

So, p=mv which would be p=(5/32)(5.4) which equals .84375.
Then, F=Pf-Pi/delta T, which would be (0)-(.84375)/(.00081)-(0), which would equal -1041.67 N, but you can't have a negative force can you? Am I doing this right, or am I missing something?

 

[LowlyPion]

So, p=mv which would be p=(5/32)(5.4) which equals .84375.
Then, F=Pf-Pi/delta T, which would be (0)-(.84375)/(.00081)-(0), which would equal -1041.67 N, but you can't have a negative force can you? Am I doing this right, or am I missing something?

Which direction did you choose as + ?
And what is the question asking?

What force did the nail recieve?

So if the impact of the hammer resulted in a (-) force to the hammer that sounds like it received an upward force and the nail received a downward force.