Download F - Intel

Ph i Review
Physics
R i
What Are Newton's Laws of Motion?
Copyright © 2010 Intel Corporation. All rights reserved. Adapted with permission. Intel, the Intel logo and the Intel Education Initiative are trademarks of Intel
Corporation or its subsidiaries in the U.S. and other countries.
*Other names and brands may be claimed as the property of others.
Forces
 “Push or Pull” that acts between two bodies
–
–
–
–
–
–
–
Tension
Gravitational force
Frictional force
Air resistance
Electrostatic force
Strong nuclear force
Weak nuclear force
Copyright © 2010 Intel Corporation. All rights reserved. Adapted with permission. Intel, the Intel logo and the Intel Education Initiative are trademarks of
Intel Corporation or its subsidiaries in the U.S. and other countries.
*Other names and brands may be claimed as the property of others.
The SI unit for force is the
Newton (N). This unit is
equivalent to 1 kgm
2
s
Phabulous Physics: Newton’s Laws
N
Newton’s
’ Fi
First L
Law
 “Law of Inertia”
 An object will continue in its state of
motion unless compelled to change by a
force impressed upon it
it.
 What net force is required to maintain a
5000 kg object moving at a constant
velocity of magnitude 7500 m/s?
–
Net force of 0  constant motion
Copyright © 2010 Intel Corporation. All rights reserved. Adapted with permission. Intel, the Intel logo and the Intel Education Initiative are trademarks of
Intel Corporation or its subsidiaries in the U.S. and other countries.
*Other names and brands may be claimed as the property of others.
Phabulous Physics: Newton’s Laws
N
Newton’s
’ Thi
Thirdd Law
L
 For every action, there is an equal, but
opposite, reaction.
Copyright © 2010 Intel Corporation. All rights reserved. Adapted with permission. Intel, the Intel logo and the Intel Education Initiative are trademarks of
Intel Corporation or its subsidiaries in the U.S. and other countries.
*Other names and brands may be claimed as the property of others.
Phabulous Physics: Newton’s Laws
W i h
Weight
 The weight of an object is the gravitational
force exerted on it by
y Earth ((or whatever
planetary mass the object is on).
 What is the mass of an object that weighs
500 N?

Fw
mg
m
Fw 500 N

 51 kg
m
9.8 s 2
g
Copyright © 2010 Intel Corporation. All rights reserved. Adapted with permission. Intel, the Intel logo and the Intel Education Initiative are trademarks of
Intel Corporation or its subsidiaries in the U.S. and other countries.
*Other names and brands may be claimed as the property of others.
Phabulous Physics: Newton’s Laws
Oh E
Other
Examples
l
 A book with a mass of 2 kg rests on a
table. Find the magnitude
g
of the force
exerted by the table on the book.
FN
Fg  mg  FN


Fg  2 kg 9.8 sm2  20 N  FN
Fg
Note: This force is called the Normal force
because it acts perpendicular to the contact
surface of the object.
object
Copyright © 2010 Intel Corporation. All rights reserved. Adapted with permission. Intel, the Intel logo and the Intel Education Initiative are trademarks of
Intel Corporation or its subsidiaries in the U.S. and other countries.
*Other names and brands may be claimed as the property of others.
Phabulous Physics: Newton’s Laws
Oh E
Other
Examples
l
 A can of paint with a mass of 6 kg hangs
from a rope.
p If the can is to be pulled
p
upp to
+
a rooftop with a constant velocity of 1 m/s,
direction
what must the tension in the rope
p be?
FT
FT  Fg  mg


F T  6 kg 9 .8 sm2  59 N
Fg
Copyright © 2010 Intel Corporation. All rights reserved. Adapted with permission. Intel, the Intel logo and the Intel Education Initiative are trademarks of
Intel Corporation or its subsidiaries in the U.S. and other countries.
*Other names and brands may be claimed as the property of others.
Phabulous Physics: Newton’s Laws
Fi i
Friction
 Friction is a contact force that is parallel to the
contact surface and perpendicular to the normal
force.
force
 Static friction (Fs) occurs when a force tries
unsuccessfully to set a body in motion.
 Kinetic (sliding) friction (Fk) occurs when a force
acts on a body in motion.
 Generally Fs >Fk
Copyright © 2010 Intel Corporation. All rights reserved. Adapted with permission. Intel, the Intel logo and the Intel Education Initiative are trademarks of
Intel Corporation or its subsidiaries in the U.S. and other countries.
*Other names and brands may be claimed as the property of others.
Phabulous Physics: Newton’s Laws
F i i Equations
Friction
E
i
Fs
(max)
  s FN
Fk   k FN
  represents the coefficient of friction - a
number that is related to the nature of the
surfaces in contact with each other.
 Fs has a range of values dependent on the
magnitude of the horizontal force being
pp
applied.
Copyright © 2010 Intel Corporation. All rights reserved. Adapted with permission. Intel, the Intel logo and the Intel Education Initiative are trademarks of
Intel Corporation or its subsidiaries in the U.S. and other countries.
*Other names and brands may be claimed as the property of others.
Phabulous Physics: Newton’s Laws
F i i Problems
Friction
P bl
 A crate
t off mass 20 kg
k iis sliding
lidi across a
wooden floor. k between the crate and
th fl
the
floor is
i 0.3.
0 3 Determine
D t
i the
th strength
t
th off
the force acting on the crate.
FN F k   k FN   k mg
F k  0.3 20 kg 9.8
Fk
F
Fg
m
s2

59 N
If the crate is being pulled
by a force of 90 N
(parallel to the floor), find
the acceleration of the
crate.
Fnet  F  F f  90 N  59 N  31N
Fnet
Fnet 31N
 ma a 

 1.6 sm2
m
20kg
Copyright © 2010 Intel Corporation. All rights reserved. Adapted with permission. Intel, the Intel logo and the Intel Education Initiative are trademarks of
Intel Corporation or its subsidiaries in the U.S. and other countries.
*Other names and brands may be claimed as the property of others.
Phabulous Physics: Newton’s Laws
F i i Problems
Friction
P bl
 A crate
t off mass 100 kkg rests
t on th
the fl
floor.
s is 0.4. If a force of 250 N (parallel to
th fl
the
floor)) is
i applied
li d to
t the
th crate,
t what
h t is
i the
th
magnitude of Fs on the crate?
  s FN   s mg
F s, max
FN


m




100
kg
9
.
8
 390 N
F s, max 0.4
s2
Fs
Fg
F NOTE: Remember that Fs represents a range of
values. In this case, the applied force of 250N
iss less
ess than thee maximum
u Fs so thee actual
cu
magnitude of Fs is 250N.
Copyright © 2010 Intel Corporation. All rights reserved. Adapted with permission. Intel, the Intel logo and the Intel Education Initiative are trademarks of
Intel Corporation or its subsidiaries in the U.S. and other countries.
*Other names and brands may be claimed as the property of others.
Phabulous Physics: Newton’s Laws
P ll
Pulleys
 Pulleys are devices that change the
direction of the tension force in cords that
slide over them.
 In problems,
problems we generally ignore the mass
and friction associated with pulleys.
Copyright © 2010 Intel Corporation. All rights reserved. Adapted with permission. Intel, the Intel logo and the Intel Education Initiative are trademarks of
Intel Corporation or its subsidiaries in the U.S. and other countries.
*Other names and brands may be claimed as the property of others.
Phabulous Physics: Newton’s Laws
I li d Planes
Inclined
Pl
 When a mass sits on an inclined plane, its
weight
g has two components:
p
normal and
parallel to the plane.

Weight mg
mg cos  Normal force
mg sin  Parallel force

Copyright © 2010 Intel Corporation. All rights reserved. Adapted with permission. Intel, the Intel logo and the Intel Education Initiative are trademarks of
Intel Corporation or its subsidiaries in the U.S. and other countries.
*Other names and brands may be claimed as the property of others.
Phabulous Physics: Newton’s Laws
How do the laws of motion
describe everyday events?
Copyright © 2010 Intel Corporation. All rights reserved. Adapted with permission. Intel, the Intel logo and the Intel Education Initiative are trademarks of
Intel Corporation or its subsidiaries in the U.S. and other countries.
*Other names and brands may be claimed as the property of others.
Phabulous Physics: Newton’s Laws
Can the motion of any object be
predicted? How?
Copyright © 2010 Intel Corporation. All rights reserved. Adapted with permission. Intel, the Intel logo and the Intel Education Initiative are trademarks of
Intel Corporation or its subsidiaries in the U.S. and other countries.
*Other names and brands may be claimed as the property of others.
Phabulous Physics: Newton’s Laws