# Physical Science by FCWAKaXS

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```									Physical Science                                              Name:_____________________
Friction                                                      Date:______________________

Background:

Friction is a force that resists ________________. It is caused by the interaction of 2 _____________.

A book is sitting on a table. Imagine you are pushing it so that it slides across the table to the right
with a constant velocity. Draw the force diagram of the situation. Label each force. (Hint: you will
have 4 forces):

1. According to Newton’s First Law, if the block is moving with a constant velocity, the net force
on the block (in the horizontal direction) is ________________________.
2. Your answer in question 1 tells you that the force of friction on the block is the same as what
other force? ______________________.
3. Using a spring scale, how could we measure the force of friction on a block of wood?
____________________________________________________________________________
____________________________________________________________________________

Objective of Lab:
To determine factors that influence the amount of friction on an object.
We will answer the following questions:
(1) How does mass of an object affect amount of friction it experiences?
(2) How does surface on which an object is sliding affect the amount of friction it experiences?

Activity 1:
How does surface TEXTURE affect the amount of FRICTION?
In this portion of the lab, we will slide the same weight across different surfaces and find the force of
friction.

What is the independent variable? ______________

What is the dependent variable? ______________

Place the friction board flat on the lab bench. Feel each of the surfaces on the friction board.
Predict: Which one do you think will cause the greatest amount of friction for the block of
wood?____________ Which one do you think will cause the least?_______________

1
Place the block on the first surface and set two 100g masses on top. Hook the spring scale to the block
of wood and pull it slowly across the surface. Read the spring scale while the block is moving at a
constant velocity. Record your data in the table below:

Cardboard             Sandpaper               Rubber                  Cork

Force of Friction
on Block & 200g

Questions:
2. Which surface created the least friction? ____________________
a. How could you tell?_____________________________________________________
____________________________________________________________________________
4. Which surface created the most friction?__________________
a. How could you tell?_____________________________________________________
____________________________________________________________________________
6. Imagine you must move a large sofa (that is too heavy to lift) in your house. You can either
push it over the carpet in the living room, or over the tile in the hallway. Which route do you
think will have the least friction? ________________________________ Why? ______
______________________________ Which route would you choose? __________________

Activity 2:
How does MASS affect the amount of FRICTION?
In this portion of the lab, we will slide different masses across the same surface and find the force of
friction in each case.

What is the independent variable? ______________
What is the dependent variable? ______________
Name two things that must remain constant in this experiment ______________________________
_________________________________________________________________________________
Predict: Will a bigger mass have more friction or less friction? _________________________
You may choose any one surface (cork, rubber, sandpaper, or cardboard) to use in this activity. With
your group select the surface you will use and write it here ________________________________

2
Place the block on your surface and set one 100g mass on top. Hook the spring scale to the block of
wood and pull it slowly across the surface. Read the spring scale while the block is moving. Record
your data in the table below. Repeat adding 100g masses to complete the table:

Block with 100g         Block with 200g       Block with 300g        Block with 400g
Force of friction
(N)

Questions:
1. Do the results of the experiment match your prediction? _______________________
2. Which mass had the most friction? ____________________________
3. Which mass had the least friction? ____________________________
4. If you did this experiment again on a different surface, which mass do you think would have
the most friction? _______________________ The least? __________________________
5. If a large whale with a mass of 1000kg and a salmon with a mass of 10kg were laying on the
same surface, which would experience more friction? ____________________________
Why? __________________________________________________________________

Applying the Concepts:
1. A train is traveling east along its track. In which direction is the force of friction
acting?_____________
2. Sketch a force diagram of the train: (you will have 4 forces)

3. The train if it is traveling at a constant velocity
a. According to Newton’s First Law, the net force on the train = _________________