can the length of the handle on a hammer affect how well it can drive a nail into a piece of wood?
Introduction
Archaeologists tell us that about 35,000 years ago, people discovered that hafting a stone axe head by putting a handle on it gave them a distinctive advantage over simply holding the stone tool in their hands. Today, we take this simple innovation for granted. Without handles, tools such as hammers, hatchets, and cleavers would be much harder to use. A handle acts like a lever. All levers have a point on which they pivot: the fulcrum. in the case of a hammer handle, the fulcrum is the wrist of the person holding the hammer. if the person changes the position of the handle, he or she changes the location of the fulcrum. This affects how easily the tool will work. in this activity, you will test to see why a handle is an important addition to tools that you strike with and how changing its length affects how easily you get work done.
Time Required
30 minutes
Materials
● hammer
● 3 large nails (10d or larger) that are all the same size
● 3 pieces of 2-in. x 4-in. (5-cm x 10-cm) wood, each about 6 in. (15 cm) long
● ruler
● safety goggles
● work gloves
Safety Note This activity requires adult supervision. Make certain that you and anyone near you are wearing goggles and work gloves during this activity. Please review and follow the safety guidelines.
Procedure
1. Put on the work gloves and goggles. Using the ruler, measure the three nails to make sure they are the same length.
2. Pick up the hammer and hold it so that you are grasping the head directly. The handle should be pointed away from you (see Figure 1). Use your other hand to hold one of the nails steady in the center of one of the wooden blocks. Give the nail fi ve blows with the hammer. Be careful not to hit your fingers. After you have struck the nail fi ve times, use the ruler to measure how much of the nail is sticking out of the wood.
3. Take a second nail and block of wood. This time, hold the hammer by the handle, grasping the handle at the mid point. Give the nail fi ve blows with the hammer. After you have struck the nail fi ve times, use the ruler to measure how much of the nail is sticking out of the wood.
4. Take the last nail and block of wood. hold the hammer by the handle again, but now grasp the handle near its end. Give the nail fi ve blows with the hammer. After you have struck the nail fi ve times, use the ruler to measure how much of the nail is sticking out of the wood.
Analysis
1. Based on your data, how did changing the length of the hammer handle change the effi ciency of the hammer?
2. in which trial did the hammer feel most comfortable in your hand? Why?
3. in which trial did the hammer get the most work done? how do you know?
4. if you were going to chop down a tree, which type of axe handle would you want to use, a long one or a short one? Why?
What’s Going On?
When you use a hammer, the handle acts as a lever. A lever has two arms. The effort arm is the end to which you apply the force.
The resistance arm is the end at which the force is directed. in the case of the hammer handle, your wrist is the fulcrum, and your own arm is the effort arm. The hammer handle acts as an extension of your own arm. The longer the handle, the greater the force directed to the head of the hammer. Yet, the lever is not providing “free energy.” When you swing a hammer with a longer handle, you have to move it a greater distance. That extra distance translates into extra force.
in addition to getting more power out of the hammer, holding a handle toward the end also gives you more control over the tool. This cuts down on wasted motion.
Our Findings
1. In general, a longer handle on a device (such as a hammer) allows the user to gain more power with each stroke. Longer handles make devices more efficient.
2. The comfort when using a tool depends on the user. In general, a tool is most comfortable in a user’s hand when it is balanced. So the hammer might feel most comfortable when you are holding it near the mid point of the handle.
3. The most work should have been accomplished in the third trial, when the length of the handle was the longest. The trial data should have shown that the nail was driven into the wood deeper on this trial, compared with the first two trials.
4. An axe with a long handle has a greater mechanical advantage over an axe with a short handle.
Classes of Levers
Not all levers are created equally. Scientists have separated levers into three classes, based on where the fulcrum is and how the forces are applied. In a first-class lever, the fulcrum is between the load and the effort. In this type of lever, the effort force and the resistance force go in the same direction. Pliers and a balance scale are examples of first-class levers.
In a second-class lever, the fulcrum is at one end and the load is between the fulcrum and the point at which the effort is applied. The resistance force and the effort force go in opposite directions. A wheelbarrow is an example of a second-class lever; the wheel is the fulcrum.
In a third-class lever, the effort is applied between the fulcrum and the resistance. Like a second-class lever, the resistance force and the effort force work in opposite directions but the point at which the effort is applied is located between the fulcrum and the resistance. The user has to apply an effort force that is greater than the resistance force. The hammer that you used in Experiment 5: Testing Hammer Handle Length is an example of a third-class lever. The advantage of this type of lever is in the extra control that you gain. One of the most important examples of a third-class lever is the handle that flushes most toilets.
