After this activity, students should be able to:

[Hit a stationary block on the floor with a meter stick - simulating hockey - and ask the class if they see energy being transferred.]

You might not be able to see it, but energy is in fact being transferred. Before we start to look at the transfer of this energy, what do you think energy is? [Your class should be able to name off food for animals and sun for plants as examples of energy]

Energy is the ability to do work. For example, if you do not eat for a long time, you get tired and it gets hard to finish your homework. If I did not have food in my body, I would not have had the energy to hit the block. As we were discussing earlier, there are many different kinds of energy. When we talk about the transfer of energy, we need to understand potential energy, kinetic energy, and thermal energy. Energy is never lost; it transfers from one object to the next and from one type to another.

Potential energy is the energy you get from position. Has anyone been told they have potential? [Students should explain that potential is the power or ability to do something]. For example, if you're standing on the ground and you're holding a ball, it does not have that much potential energy, because it is not that high. But if you were standing on the tenth floor, the ball would have a high potential energy, because if you were to drop it, it would have a long way to go down. So when I lifted the stick, I gave it potential energy.

If we take it step by step, we can track the energy as it flows. If I drop the ball, it will start falling and moving. When the ball is dropped, the potential energy becomes kinetic energy. Kinetic is a word used to talk about motion. In the other example, first I lifted the meter stick which gave it potential energy. Now that my stick has potential energy, if I let it go, it will start moving. When an object moves, it has kinetic energy. The faster it goes, the higher its kinetic energy is. A hockey player makes the stick move faster, giving it even more kinetic energy by applying a force in addition to gravity. This energy is transferred when it hits the block. Why don't you try to explain to me what has happened with the energy so far. [Have the class explain their understanding of potential and kinetic energy and how it has transferred.]

Now the block has been hit - it has energy too. And since it is moving, it is kinetic energy. And if I do it again [hit the block again], can you notice if it is getting faster or slower? It looks to me like it is slowing down. So you could say it is losing its kinetic energy. But where is that energy going? If we think about it, what is the only thing that the block is touching? You're right; the floor is where the energy is transferred. And what kind of energy is this? Well, it cannot be potential or kinetic, because the floor cannot move. But something is moving on top of the floor. Let's try this ourselves. Can you rub your hands quickly on your legs? Do you feel it getting hotter? That is what happens to the floor, the block is rubbing on it. And even though you probably cannot feel it, the floor is getting hotter. This kind of energy is called thermal energy - makes sense, because thermal is an adjective to describe temperature. Some scientists also call it heat energy, but it means the same thing. And you might have heard thermal energy talked about as friction. Friction is the loss of kinetic energy into thermal energy which is why the block slows down.

So let's think about this - can you relate this to hockey? The players each have a hockey stick and they want to hit the puck into the goal. But I have just been told that engineers are trying to design a hockey game to play inside where there is no ice. And this means that they need to come up with new pucks. So I was thinking that we should try to design the "best" puck.

Background

Create a Hockey Puck Testing Device

The goal of the testing device is to ensure the hammer delivers approximately the same impact to each of the experimental pucks. An example of a testing device is shown in Figure 3 above. In the picture, a hammer is suspended from a rod using string. The rod is suspended between two chairs. In order to make this testing device follow these steps. Figures 3 through 7 are also linked as higher resolution attachments (see Attachments section below).

Figure 3 click for copyright

1. Take a loop or two of string and attach it to both sides of a hammer handle as shown in Figure 4.

   Figure 4 click for copyright

2. Insert a rod long enough to span the distance between two chairs through the loop and rest it on two chairs as shown in Figure 5. The rod could be a wooden dowel, a strong yardstick, a small pipe, or even a long screwdriver as shown.

   Figure 5 click for copyright

3. Attach the rod to the chairs using duct tape to secure it. The hammer should swing on the rod without the rod moving.
4. Move the chairs so there is a wall behind them limiting the distance the hammer may be pulled back prior to release as shown in Figure 5 and Figure 6. This way, the amount of initial potential energy from lifting the hammer will be consistent between tests.

   Figure 6 click for copyright

That's it. There are many variations to this depending on what is available in the classroom. Rather than using string, the same thing could be done using a large binder clip instead of string (see Figure 7).

Figure 7 click for copyright

Before the Activity

With the Students

Make sure to keep the hammer testing device away from unattended students.

How would increasing the height of the hammer affect the distance the puck travels? Why? [Answer: The more height, the more initial potential energy, the more energy to transfer to the puck, so the puck will travel farther.]

A shuffleboard game can be made by placing lines with masking tape on the floor. On each side of the 5 meter "court," place three lines of masking tape on the ground separated by half a meter. The teams will sit on each side of the court and try to slide their puck into the opposing teams scoring zone. One point will be awarded for landing the puck between the middle line and the close line, and 3 points will be awarded for landing the puck between the far line and the middle line. The first team to reach 10 points will win.