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Physics, Mr. Kent
Daily Worksheet: Friction
Name: ____________________________________
1. A ball rolling on a horizontal surface slows down because of ____________ between the
_______________ and the __________________.
2. A sky diver slows down because of _______________ between the ____________ and
the ___________________. That is, ________________________ is a type of friction.
3. Friction is a _________________.
4. Friction is a ____________ that __________________ motion.
5. So if an object moves East across a surface, the force of friction is exerted __________.
If a force is directed to the right, the force of friction is exerted ___________________.
6. Draw the diagram on the board.
Then: Fnet = _______________
Calculate acceleration of the block.
7. It’s harder to ____________________________________ over a surface than it is to
____________ that same object moving over the same surface.
8. There are two types of friction. Circle the one that is larger.
Movement
Friction
9. Symbols for friction: Static Friction: ________ Kinetic Friction: _________
10.Draw 2 free body diagrams, label the forces. Use a thicker arrow for a larger force: A
gnome pulls on a block across a surface. Drawing 1: His force just before the block
moving. Drawing 2: Later he moves the block across the floor with less force.
11.___________ friction is an ________________ force because it’s ________________. If
an object on a surface is pushed or pulled with a ____________ force, static friction will
push back with that ____________ force. Since the 2 forces _____________ they are
__________________ and the object doesn’t _______________. Static friction will
______________ and continue to ____________ the push or pull until the push or pull
reaches its __________________. Only then will the object _______________.
12.A 200 kg block rests on a cement floor. The maximum static friction between the block
and the floor is 350 N. Complete the following table:
Push or Pull Force
Static Friction (fs)
Net Force (Fnet)
Movement
100 N
200 N
300 N
400 N
At what rate will the block accelerate with a push pr pull force of 400 N? _____________
13.Order these from lowest friction to highest friction: ________________________
a.
b.
c.
d.
90 kg block of wood on a cement floor
50 kg block of wood on a cement floor
50 kg block of wood on ice
50 kg block of ice on ice
14.What, then, are the two factors that affect friction?
a. _____________________________________________________________
b. _____________________________________________________________
15.Different ____________ of surfaces have different amounts of ______________. The
amount of friction from a pair of __________________ is indicated by the pair’s
_________________________ of ____________________.
16.The greek letter ______ (________) is used to represent coefficients of ____________.
17.Symbols:
a. Coefficient of static friction: _________ Coefficient of static friction: _________
18.Refer to this table of coefficients of friction regarding pairs of surfaces:
Pair with the greatest static friction:
___________________________
Pair with the greatest kinetic friction: ___________________________
Pair with the smallest static friction: ___________________________
Pair with the smallest kinetic friction: ___________________________
Does the highest static friction always mean the highest kinetic friction? __________
19.Whenever a force is exerted on a ______________ the surface pushes back with a force
called the ______________ force (________).
20.The most common force on a ______________ is an object’s ________________. When
an object is on a surface its weight pushes _____________ and the surface exerts a
_________________ up equal to ___________________. If the surface is
__________________ then:
a. The forces are _____________________________
b. The object is in ________________________________
c. The object doesn’t ________________________
21.Normal Force is _____________________ to the surface that exerts it. So, if an object
rests on a ___________________________ surface, then _______ does not equal the
object’s ________________.
22.In most of our problems, objects will reside on ________________________ surfaces.
So, _____________ = _______________ and we can use _______________ in our
friction calculations.
23.A 90 kg block sits on a horizontal surface. Weight? _________ Direction: _________
Normal force (FN)? _________ Direction: _________
24.Formula for Static Friction: _______________ For Kinetic Friction: _______________
25.A 200 kg steel block sits on a copper surface.
a. �s = _________________
�k = __________________
b. FN = _______________
c. fs = _________________
fk = _____________________
26.Chelsea exerts a force of 800 N to pull a 125 kg aluminum block across a steel surface.
FN = __________ fs = __________ Will the block move? _______
fk = __________ Fnet while moving = ________ Acceleration = ________
27.Franky exerts a force of 725 N to pull a 75 kg glass block across a glass surface.
FN = __________ fs = __________ Will the block move? _______
fk = __________ Fnet while moving = ________ Acceleration = ________
Physics, Mr. Kent
Classwork: Friction
Name: _______________________________________________
1. Friction is a ____________________________________
2. Definition of friction: ____________________________________________________
3. There are two types of friction:
a. _____________________________ occurs when an object is ________________
b. _____________________________ occurs when an object is ________________
4. Which type of friction is larger? ____________________________________________
5. So, if you push a desk across a floor, which requires more force? (a) Getting the desk
moving (b) Keeping the desk moving. ____________ Explain:
6. Kayla decides to push 200 kg bookshelf across the tile floor of her basement. She has to
push very hard (F = 300 N) to get the bookshelf moving. Once it is moving, however,
pushing it it fairly easy (F = 175 N). She keeps pushing, however at 300 N.
a. Maximum static friction: ____________ b. Kinetic Friction: ____________
c. . FNet while moving: _____________ d. Acceleration of the shelf: ____________
7. Kayla thinks back to exactly what she did. At first, she pushed with a small force (100
N). When this didn’t work she pushed progressively harder: With a force of 175 N then
250 N and finally 300 N. Complete the following table
FPush
fs
FNet
Movement
8. When an object sits on a surface the force of its ________________ is exerted
____________________ on the surface. We know from Newton’s 3rd Law that for
every force there is an _______________________________________________. What
is the name of the equal and opposite force to the weight of an object sitting on a surface?
______________________. Abbreviation: _______________
9. A 75 kg object rests on a horizontal surface:
a. The object’s weight:
Magnitude ___________ Direction: _____________
b. The surface’s normal force: Magnitude ___________ Direction: ____________
c. Symbol: For Normal Force: ___________ Net Force: _____________ These are
similar. But can you see the difference? _________
d. Net force on the 75 kg object: ______________. The forces are _____________
and the object is in _____________________. It doesn’t _________________.
10.When an object slides over a surface we have a pair of surfaces: The bottom of the
__________________ and the ______________________ itself.
11.Do all pairs of surfaces display the same amount of friction? ____________. What
constants indicate the amount of a pair’s friction? ______________________________
12.Provide the coefficients of friction for these surface pairs:
Surface 1
Surface 2
Copper
Steel
Steel
Aluminum
Zinc
Cast Iron
�s
�k
13. Liam uses a winch to exert 3,100 N of force to pull a 300 kg block with a rubber bottom
over a dry cement floor. FN = ___________ fs = _____________
Will the block move? ________ fk = _____________ a = _____________
14.1,345 N is required get a 225 kg resting on a surface moving. What is coefficient of
static friction? _______. What is the surface pair? _____________________________
Physics, Mr. Kent
Daily Worksheet: Friction #2
Name: ______________________________________________
1. Friction is a ________________ that _________________ motion. If a force is exerted
South on an object then friction is exerted ________________
2. A person pushes a box across a garage floor. Object exerting the push: ______________.
Object exerting the frictional force: _______________________
3. There are 2 types of friction. If an object is stationary on a surface, that surface exerts
_________________ (_____). If an object is sliding over a surface (is moving) then the
surface exerts _________________ (_____). Which of these frictions is larger?
________________. That matches your experience, right? It’s harder to ____________ an
object moving than it is to ____________ it moving.
4. An object resting on a horizontal surface exerts a force down on the surface. The best name
for that force: _________________. The surface exerts a force up called the ____________
_______________ which is equal to _________________. The forces are ______________,
the object is in ______________________ and it does not _______________.
5. ________________________ of ________________ tell you how much friction exists
between a ___________ of ________________. The greek letter ________ (_____) is used
for these coefficients.
a. Stationary objects:
__________________________________, ___________
b. Moving objects:
__________________________________, ___________
6. Formula, Static Friction: ____________________ Kinetic Friction: ___________________
7. A 4.5 kg block of glass is pushed over a copper surface with a force of 70 N.
FN = ______________ fs = ___________ Will the block move? ______ fk = _________
FNet while moving? ___________ Acceleration? __________
8. In this formula, which variables on the right are “variable” and which is/are constant:
fs = µs m g
So, what 2 factors affect friction? _________________________ and ____________
9. Complete this table to describe the difference surfaces/different masses demo:
Surface 1
Surface 2
Mass
fs
fk
10.We’ve already broken friction down between Static and Kinetic Frictions. There’s another
way to break friction down: Between _________________ & _________________ friction.
____________________ is always greater.
11.Complete this table to describe the sliding vs. rolling friction demo.
Description
Kinetic Friction
12.Both __________________ and ____________________ friction opposes you when you
push a car from rest. Obviously, the tires along the road have ________________ friction.
But inside the car, many surfaces ______________ over each other. In fact, most of the
friction opposing you when you push a car from rest is _____________________________.
Physics, Mr. Kent
Working Friction Quiz
Name: ____________________________________________
1. Julien (75 kg) stands on a horizontal surface. Draw a free body diagram for Julien. Label
each arrow with the name of the force and its magnitude.
2. A 150 kg cast iron block sits at rest on a horizontal copper surface. fs = ________________
fk = ____________ How much force must exerted: To move the object: _______________
To keep the block moving once it is in motion? ________________
3. A force of 1,700 N is exerted on the block of problem #2. Will the block move? _________
If so, what is the net force on the block while it’s moving? ____________
At what rate will the block accelerate? _______________
4. A force of 150 N is used to move a 15 kg block of steel over a steel surface. How far will
the block move in 40 seconds? At what velocity will it be travelling at that time?
5. Robert exerts a force of 200 N on a 40 kg block of unknown substance on a surface of
unknown substance causing it to accelerate at 0.216 m/s2. What is the net force exerted on
the object while it’s moving? ___________. fk = ___________ µk = __________
What is the pair of surfaces? _________________________________________