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# PreLab

Friction plays the role of both hero and villain in our world. Activities like walking and eating would be impossible without it. Nails would slip from boards, knots would come untied, and hair clips would fall out if it weren’t for friction  On the other hand, skinned knees, scuff marks on floors, and wear and tear of moving parts are caused by friction. Learn about this force then decide if you think friction is a hero or villain.

### BRANCH OUT

Transportation engineers design roads to provide the right amount of friction. They know that friction provides traction and control for a safe driving experience, especially in icy or wet conditions.

### GET FOCUSED

This Investigation is designed to help you to answer the following Focus Questions:

• What is the relationship between speed, velocity, and acceleration?
• How does the frictional force affect motion?

Note: These questions are located in your  SDR at the beginning and end of the Investigation.

### GO DEEPER

As a class, read the Background(s) in Investigation 1. When finished, discuss the following concepts as a class:

• A force is a kind of push or pull on an object.
• A force has two qualities: direction and magnitude.
• Velocity is a measure of the speed of an object that is moving in a specific direction.
• Acceleration measures the change of speed of an object that is moving in a specific direction.
• Acceleration is a change in velocity.

### LEARN THE LabLearner LINGO

The following list includes Key Terms that are introduced in the Investigation Background(s). They should be used, as appropriate, by teachers and students during everyday classroom discourse.

• force
• velocity
• acceleration
• applied force

Note: Definitions to these terms can be found on the Introduction page to the CELL.

Note: Additional words may be bolded within the Background(s). These words are not Key Terms and are strictly emphasized for exposure at this time.

### SET FOR SUCCESS

• This CELL will focus on forces, motion, velocity, and acceleration. You will perform experiments to better understand how those concepts are related.
• Complete the Recall section in your SDR.
• A force is a kind of push or pull on an object. A force causes an object to accelerate in the direction of the force.
• Scientists use a different definition of velocity than people may use in everyday language.
• This understanding of velocity will be important throughout this CELL.
• Play the video below. Remember to follow along with your SDR and make any notes that you think might be helpful in the lab.
• After the video, divide into your lab group to discuss strategy for the lab. For example, you may assign certain group members to perform specific functions during the lab.

Note: The purpose of the video is to allow you to anticipate the laboratory experience you will soon encounter. You should leave this PreLab session with a firm idea of what to expect and how to perform in the lab.

Note: Homework is posted below the video.

### HOMEWORK

You should review the Investigation and video in preparation for the Lab.