Most of you have probably had the opportunity to drive a nail into a piece of wood using a hammer. In this problem we will explore some of the physics involved in this action as well as the physical properties of the nail and hammer. Assume that both the hammer and nail are made of steel.
1. Describe the forces acting between the nail and hammer during the collision between the two. To be specific assume that you are driving a vertically oriented nail, with its pointed end down and its head up, into a horizontal block of wood.
2. The nail is a straight rod with a cone shaped point on the end. Describe the force that the nail's point exerts on the wood when you hit it with the hammer from above.
3. As you drive the nail into the wood it may bend if you don't hit is squarely with the hammer. Describe the plastic deformation that allows the nail to bend.
4. After bending the nail you straighten it out and try again, but it bends again. This time when you try to straighten the nail, it breaks. Why?
5. If you try to drive a standard nail into concrete, which is much harder than wood, you probably won't get very far before bending the nail. However, you can buy special nails designed to be driven into concrete. Compare the yield strengths of the two types of nails.
6. After driving one of these special nails into concrete, you may notice that the head of the hammer has lots of small dents. How could heat be used to make the hammer head more resistant to this denting?
7. Hardening the hammerhead (as in question 6) might not be a good idea. If the hammer is unable to yield (dent) when it strikes a hard object something more catastrophic may occur. If the hardened hammer is deformed, but unable to yield, what is likely to happen?
8. How could you use heat to reverse the hardening produced in question 6?