Friction Lab

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Objective

SWBAT create a definition for friction and explain its effect on motion.

Big Idea

By observing a demo and collecting data, students will create their own definition for friction.

Engage

5 minutes

This lesson addresses friction and its effect on motion.  MS-PS2-2 is addresses through this activity because students are making sense of the forces that can affect an object's motion.  They are also writing about friction in a way that creates an opportunity to address SP-8, by obtaining observational data and communicating that to others through the creation of a definition of friction.

For the demo you will need: two wood blocks of equal size, a square of sandpaper, and a smooth table surface. 

For the lab activity (EXPLORE) you will need: a ramp, a cart, a square of sand paper, a measuring tape, a timer for each small group.

To start the lesson, I show the students the wood blocks and the sand paper and ask them to predict the following in their student notes sheet:

Describe what will happen when I push a wood block on two different surfaces.

Wood block on a smooth table:

Wood block on sand paper:

For students who have trouble imagining the scenario, have them touch the smooth table and then touch the sandpaper to make a prediction.  Ask 2-3 students to share responses when they are finished writing. 

Explore

10 minutes

For the next part, I actually show them the wood blocks moving on the different surfaces: smooth wood table versus the sandpaper. I push the wood block on the table first. Then, I push the wood block on the sand paper, exaggerating the struggle. I ask them to respond to the following prompt in their notes sheet during the demonstration:

Make observations and inferences about what you observe during the demo.

Wood block on smooth table:

I saw…

I think this happened because…

Wood block on sand paper:

I saw…

I think this happened because…

After the kids have had sufficient time to record their responses, I ask a few to share out. 

Explain

10 minutes

This section of the lesson serves as a mini check for understanding of what they've seen regarding friction thus far.  By responding to the following prompt, students are engaging in an initial conversation about friction based on their observations and inferences regarding the demonstration.  

With your table mates, write down what you know about friction so far.

From the wood block demo, we know that… (makes it harder for things to move)

What does friction do? (makes things move slower)

Where does friction come from? (rough surfaces)

What would happen if there were no friction? (things would move faster)

 

After 7-8 minutes, I ask 1 person from each group to share their table's responses with the class. 

Elaborate

15 minutes

Now, the students will test their ideas of friction by recording data evidence using the ramp and the cart. By following the procedure below, students record their data and identify that the cart moves slower over the sandpaper than over the smooth floor, thus proving friction makes objects move slower. 

Follow the procedure for the lab below. Record all data.

Materials: cart, ramp, sandpaper, timer, measuring tape

Procedure:

  1. Measure the distance from the top of the ramp to the piece of tape on the floor.

  2. Put the cart on the highest release point on the ramp.

  3. Start the timer and release the cart.

  4. Stop the timer when the cart reaches the front of the piece of tape.

  5. Repeat this without the sandpaper.

Data:

Distance from top of ramp to tape:

Time for cart with sandpaper:

Speed:

Distance from top of ramp to tape:

Time for cart with NO sandpaper:

Speed:

Analysis:

  1. When did the cart go faster, with sandpaper or without?

  1. What do you think made the cart move slower with the sand paper?

  1. How could we make the car move even slower?

 During this time, I move from group to group ensuring proper following of the procedure and making sure they understand why the sandpaper is causing the cart to move slower. 

Evaluate

5 minutes

For the last part, students will work individually to create their own idea of friction based on observational data in the demo and in the lab activity.  

Based on your observations from the demo and from the lab, write a definition for friction and explain its effect on motion.

Friction makes objects… (move slower)

I know this because... (when we put the block on the sandpaper, it moved slower and when we put the cart over the sandpaper the speed was less than on the smooth floor)