Friction- Day 1

Introduction

Welcome to your Friction WebQuest!

In this WebQuest, you will explore

  1. What is friction
  2.  Types of friction
  3. What is the coefficient of friction
  4. How to find out the amount of force that friction applies to objects.

Standards:

NGSS HS-PS2-1: Analyze data to support the claim that Newton’s second law of motion describes the mathematical relationship between the net force on a macroscopic object, its mass, and its acceleration.

 

Task

Task 1: Do Now (5 mins)- In your worksheet



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1.  Why do you have to put water on a slip ‘n slide to get it to work?





2. How would adding soap to the slip ‘n slide affect your motion? 



Task 2: Read and annotate the passage IN YOUR WORKSHEET (7 mins)

WHAT IS THE FORCE OF FRICTION?

Friction is a force that opposes the relative motion between two objects in contact. Friction results from electromagnetic forces. It occurs as a result of the interactions between atoms on the surfaces of two objects. The rougher the surfaces, the greater the friction between them.  Friction can produce heat when surfaces rub together. For example, you can warm your hands on a cool morning by rubbing them together. The heat from friction can cause a match to light.

Even surfaces that look or feel smooth are rough at the molecular level. Interactions between atoms and molecules produce friction even between smooth surfaces. 

TYPES OF FRICTION 

There are two main types of friction: kinetic friction and static friction. Kinetic friction is the friction between two moving surfaces. There are two main types of kinetic friction: sliding friction and rolling friction. Sliding friction occurs when two objects slide past each other. Rolling friction occurs when a round object rolls over a flat surface. In most cases, rolling friction is less than sliding friction. This is why it is easier to push a chair on wheels across a floor than a chair without wheels. 

Static friction is the friction between two surfaces that are not sliding past each other. Forces act between molecules on the surface of two objects, holding them together. Static friction is usually greater than kinetic friction. Therefore, in most cases, it takes a greater force to start an object moving than to keep it moving.

How Does Friction Impact Everyday Life? 

Friction allows you to hold a pencil and use it to write on a piece of paper. Friction even keeps you from slipping when you walk. 

Friction between the tires of a car and the road allows a car to move. As the wheels of a car turn, they push against the road. As a result, the road pushes forward on the car. The force pushing the car forward must be greater than the friction that opposes the motion of the car. Due to friction, a constant force must be applied to keep the car moving. Friction also keeps cars from moving when parked. 





Check for Understanding: Answer the following - IN YOUR NOTEBOOK

  1. Which of the following changes when the material for a ramp is changed to become rougher? 

    1. Mass

    2. Gravitational Force

    3. Friction Force

    4. Both a and c

  2. What determines the value of sliding friction? Also, explain why:_______________________________________

    1. The temperature

    2. Area of Contact

    3. The roughness of the surfaces in contact

    4. The mass 

  3. What are the two main types of kinetic friction? 

    1. Static and sliding friction

    2. Rough and smooth friction

    3. Sliding and rolling friction

    4. Rolling and static friction

  4. Which of the following forces tends to be the largest? 

    1. Kinetic Friction

    2. Static Friction

    3. Rolling Friction

    4. Sliding Friction

 Vocabulary- Write down the definitions of the following 

  • Friction force

  • Intermolecular force

  • Static friction

  • Kinetic friction

  • Coefficient of friction

Task 3: Draw free-body diagrams from the following scenarios and explain it in one sentence - In your notebook (5 mins)

(Your free-body diagram must show the force vectors to the scale)

  1. A heavy wooden box is being pulled by a rope towards the right at constant velocity.
  2. A train of huskies is drawing a sled westwards at a constant velocity.
  3. A child ice-skating with constant acceleration towards the left.
  4. A parachute is accelerating(speeding up) downwards.
  5. A parachute is falling down at a constant velocity
  6. A parachute is decelerating (slowing down) downwards.
Evaluation

Day 1

Exit ticket (In your notebook)- 5 mins

A car, experiencing force F1 to the right and force F2 to the left, is drifting in the direction of force F1. While moving in this direction, the carts start to slow down. 

  1. Draw a free-body diagram modeling the forces acting on the object. Be sure to correctly label each force.

  2. Which of the following best explains the relationship between forces F1 and F2?

    1. F1 = F2

    2. F1 > F2

    3. F2 > F1

    4. Both A and B

    5. Both A and C

  3. Which force, F1 or F2, is the force of friction? Explain how you know.