# Newton s Laws powerpoint - PowerPoint

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```					TAKS Objective 5.2
questions.

   Use the formula
chart.
   Use a calculator.
   Don’t guess!
1. The diagram represents the total travel of a
teacher on a Saturday. Which part of the trip is
made at the greatest average speed?
AQ
BR
CS
D T
2.
3. How much force is needed to
accelerate a 1,300 kg car at a rate
of 1.5 m/s2?
A 867 N
B 1,950 N
C 8,493 N
D 16,562 N
4. A ball moving at 30 m/s has a momentum
of 15 kg·m/s. The mass of the ball is —

A 45 kg

B 15 kg

C 2.0 kg

D 0.5 kg
correct, try the quiz at the end . . .

1. C
2. A
3. B
4. D
Law of Conservation of Energy
   Energy can change
forms, but is never
created nor destroyed
   Loss in one form = gain
in an another form
   A falling object speeds
up as it falls to the
ground; PE decreases as
KE increases. The KE it
has at impact = the PE it
Forces and Motion
   Forces can create
changes in motion
(acceleration)
   Deceleration is negative
acceleration
   Force = Mass x
Acceleration
   Units of force are
Newtons (N)
Motion can be described simply

 Motion  is a
change in an
object’s position
 Average velocity
(speed) is a
change of the
position of an
object over time
Velocity Graphs                        V = distance
time

 Velocity(v) is                               Velocity
the slope (rise
over run) of a                   60

Distance (m)
position (d)                     40                        Series1
vs. time (t)                     20                        Series2

graph                            0
1 3 5 7 9 11 13 15
Time (sec)
The diagram represents the total travel of a
teacher on a Saturday. Which part of the trip is
made at the greatest average speed?
How do we work this one?
Calculate v = d/t for each segment.
Acceleration is a change in an objects
velocity (speed or direction)

   When an
object’s speed
changes over
time it is
accelerating (or
decelerating)
   A = vfinal – vinitial
time
   Units for
acceleration
m/s/s or m/s2
Acceleration Graphs
   Acceleration (a)                                      Acceleration
is the slope of a

Velocity ((m/s)(m)
velocity (v) vs.                         60
time (t) graph                           40
   Plotted on a                             20
distance vs. time                         0
graph,                                        1   3    5   7    9       11   13   15
acceleration is                                            Time (sec)
an exponential
curve
Definition of a Force
   A Force is a push
or a pull
Balanced Force

   A force that
produces no
change in an
object’s motion
because it is
balanced by an
equal, opposite
force.
Unbalanced Forces
Are forces
that results
in an object’s
motion being     +
changed.
Friction

A force that acts in a direction
opposite to the motion of two
surfaces in contact with
each other.
Friction
Friction causes an
object to slow
down and stop.
Since the amount
of energy stays
constant, the
energy becomes
heat.
Newton’s 1st Law of Motion

 Object   in
motion
stays in
motion
Newton’s 1st Law of Motion

And
Objects at
rest stay
at rest
Newton’s 1st Law of Motion

they are acted upon by
 Until
unbalanced forces.
Law of Inertia is another name
for Newton’s 1st Law

   Tendency for an
object to stay at
rest or moving in
a straight line at a
constant speed.
   The mass (m
measured in kg)
of an object
determines its
inertia
Unit of Force – Use the chart

 Unit of mass is kg
 Unit of Acceleration is m/s/s

 1 kg x 1 m/s/s = 1 kg x m/s/s
= 1 Newton (N)
 Resulting in Force unit called
a Newton (N)
Newton’s 2nd Law or
the Law of Acceleration
Force = Mass X
Acceleration
F=ma
Weight (pull of gravity) is a
commonly measured force,
calculated by F=mg, g is the
acceleration due to gravity 9.8
m/s2
Same floor = same friction
Same room = same air
Same car = same mass
Newton’s 2nd Law of Motion

The greater the
mass of an
object, the
greater the
force required
to change its
motion.
Newton’s 2nd Law of Motion

 Thegreater the
acceleration of
an object, the
greater the force
required to
change its
motion.

How much force is needed to
accelerate a 1,300 kg car at a rate
of 1.5 m/s2?
To solve this:

F=ma      or
= 1300Kg x 1.5m/s2
F = 1950 N
Newton’s 3rd Law of Motion
 Forevery
action force
there is an
equal and
opposite
reaction
force.
Newton’s 3rd Law of Motion

All forces come
in action-
reaction pairs
Ex: feet push
backward on
floor, the floor
pushes forward on
feet
Newton’s 3rd Law of Motion
Rocket and Jets-
walls of the fuel
compartment
push backward on
igniting gases,
gases push
forward on the
fuel compartment
(and the rocket)
so it rises.
Newton’s 3rd Law of Motion
   Rowing a
boat
 Name    the Action
Reaction pair of
forces?

Action: Oar pushes water back.
Reaction: water pushes boat forward.
Machines do Work
 Work: the product of force
times distance
W=Fxd
The work done by forces on an
object = changes in energy
for that object.
work and energy are
measured in Joules
1 Joule=1 Newton • meter
Machines make work easier
   The ideal mechanical
is the number of times the
output force is larger than
the input force
IMA=Fout/Fin
   A machine can only make this
happen by moving the input
force a farther distance than
the output force
   Fin • din=Fout • dout
Real Machines use Energy
   No real machine is
100 % efficient. i.e.
none put out more
work than is put in
   Efficiency of a
machine is work
output/work input X
100 %
   Eff = Wout X 100%
W
in
Machines use power
 Power:  the rate at
which energy is used
(work is done)
 P=Work/time

 Power is measured
in H.P. or watts
 1 watt = 1 Joule
1 sec
6 Types of simple machines
 Some   Simple
Machines:
 Inclined planes

 Screws

 Pulleys

 Wheel and axle

 Levers

 Wedge
Universal Law of Gravitation

All objects in
the universe
attract each
other by the
force of
gravity
Universal Law of Gravitation
1) the mass of the object
doing the pulling, and

Gravity varies depending
on two factors:

2) the distance from the center
of that object
On Earth gravity = 9.8 m/s/s

 Forevery
second that an
object falls its
speed
increases by
9.8 m/s
Weight= Mass (m) X
acceleration due to gravity (g)

 Weight   Unit of mass =
kg
 Unit of acceleration =
m/s/s
 Unit of weight =
Newton
pound_
Last quiz!
   For the next 7 slides, write the
this one Obj. 5.2
   If you have time, check out TAKS
Dr. Try to answer each question,
and then see the answer and why it
is correct. This is the practice test
you took in September.
   GOOD LUCK!
1. The frog leaps from its resting position at the
lake’s bank onto a lily pad. If the frog has a
mass of 0.5 kg and the acceleration of the leap
is 3 m/s2, what is the force the frog exerts on
the lake’s bank when leaping?

A 0.2 N           B 0.8 N
C 1.5 N           D 6.0 N
2. If a force of 100 newtons was
exerted on an object and no work
was done, the object must have —

A accelerated rapidly
B remained motionless
C decreased its velocity
D gained momentum
3. How much work is performed when a 50 kg
crate is pushed 15 m with a force of 20 N?
A 300 J
B 750 J
C 1,000 J
D 15,000 J
4.
5.
6. Which lever arrangement requires
the least effort force to raise a 500 N
resistance?

A.                    C.

B.                     D.
7. The illustration below shows a student
standing on a skateboard about to throw a ball.
Which picture correctly shows the movement of
the skateboard after the release of the ball?
1. C 2. B 3. A 4. C 5. A 6. A 7. D

and your teacher’s name on it.
Now its your turn. Work through
problems in the workbooks, ask for
help if you need to from any science
teacher, and attend the tutorials for
objectives on which you did not
score 100%.

```
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