can a simple stone chopper be an effective cutting tool?
Introduction
These days, humans have many tools for cutting. Knives, scissors, saws, and axes can all be used to cut, chop, and slice through fabric, rope, wood, and even steel. each of these tools is an example of a device called a wedge. Wedges are implements that are wide at one end and gradually taper to a thin edge on the opposite end.
Before people had tools made of metal, they made simple cutting tools from stone, wood, and bone. Archaeologists tell us that the fi rst tools were stone choppers, used for cutting everything from animal hides to vines. in this activity, you will test to see how effective a simple stone chopper is at cutting a piece of rope.
● round rock about the size of a fi st
● rock about the size of a fi st, with a broken sharp edge
● 12-in.-long (30-cm) piece of 2-in. x 4-in. (5-cm x 10-cm) wood or similar
wooden block
● 2 identical pieces of nylon or cotton rope, each about 24 in. (60 cm) long
● 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. Take one piece of rope and grasp it in two hands. Try to rip the rope apart. Record your results.
2. Place the wooden block on a sturdy surface (table or fl oor). drape the piece of rope across the middle of the block (see Figure 1). Grasp the round rock in one hand and carefully strike the rope where it crosses the middle of the block. do this 20 times. Make certain that when you hit the rope with the rock, you are hitting it in the same place each time. Be careful not to hit your fi ngers with the rock.
3. Pick up the piece of rope that you just hit with the rock and observe it carefully. What happened to the fi bers of the rope? Record your observations. Try to rip the rope apart again and record your results.
4. Take the second piece of rope and grasp it in two hands. Try to rip the rope apart and record your results. Place the second piece of rope on the wooden block like you did with the rope in Step 2. Pick up the rock with the sharp edge and strike the sharp edge against the rope 20 times, the same way that you did with the round rock in Step 2.
5. Pick up the piece of rope that you just hit with the sharp rock and observe it carefully. What happened to the fi bers of the rope? Record your observations and then try ripping the rope apart. Record your results.
Analysis
1. What was the effect of hitting the rope with the round rock? Why?
2. What was the effect of hitting the rope with the sharp rock? Why?
3. Based on the results of the experiment, how might you improve the cutting ability of the second rock?
What’s Going On?
in order for an object to be an effective cutting tool, at least one edge has to be wedge-shaped. The sharper the edge, the easier it will cut. Modern cutting tools have extremely sharp edges, which allow them to easily split and separate the fi bers of the material being cut. early humans discovered that rocks with natural wedge shapes were better than rounded rocks at cutting and splitting materials. Rounded rocks could break fi bers by smashing them. Wedge-shaped rocks would split the fi bers apart, making it easier to separate them.
Our Findings
1. hitting the rope with a round rock will cause some of the fi bers to break, but it will probably not break enough of them to allow you to tear the rope apart.
2. hitting the rope with the sharp edge will cause the fi bers to split and tear. This is because the wedge-shaped edge cuts through the fi bers of the rope.
3. if you wanted to improve on the cutting ability of the sharp stone, you could use another rock to chip away at the edge so that it is smoother and more tapered. The more gentle the taper, the sharper the cutting tool.
Working with Wedges
Although simple stone choppers helped early humans carry out many tasks, their cutting ability was still limited. Through trial and error, people eventually discovered that they could make a better tool by sharpening both sides of the cutting face. They did this by using another rock called a “hammer stone” to gradually chip away at the edge of the chopper. This led to the development of a more sophisticated tool known as a hand axe. Unlike a simple chopper, the hand axe had a much narrower blade that was better for cutting.
Both the chopper and hand axe are examples of wedges. Many common woodworking tools used today are simply variations on a basic wedge design. Depending on the shape of the wedge, tools can be used for cutting, splitting, or shaving wood. In Experiment 1: The Wedge Design of a Stone Chopper, we saw how a wedge could be used for cutting. In Experiment 2: How a Tool’s Wedge Shape Affects Wood Split, we’ll examine which type of wedge is best at splitting a piece of wood.
A hatchet, like an axe, is an example of a wedge, a tool that is wide at one end and narrows to a point or edge at the opposite end. It is used for things such as cutting, chopping, and slicing.
