Transcript Physics PowerPoint

Objective 5
MOTION &
FORCES
Have this on your
desk for EVERY
question involving
math.
EVERY FORMULA YOU
FORMULAS
NEED
IS ON THE CHART.
You won’t ALWAYS use all the
numbers
given.
Constants &
Eliminate
Conversionsbad answers.
ALWAYS use your calculator!!!!
Ruler
SPEED describes how fast
an object moves.
Speed (v) = Distance
Time
• Average velocity (speed) is the change of
position of an object over time. Velocity is a
vector quantity that includes direction.
Acceleration
a =final velocity – initial velocity
∆T
Acceleration
Velocity ((m/s)(m)
Change in velocity over
change in time
(slope)
60
40
20
0
1
3
5
7
9
Time (sec)
Units for acceleration m/s/s or m/s2
11
13
15
The speed of sound in human
tissue is about 1600 m/s. If an
TIME
ultrasound pulse takes 1.5 x 10-5s
to travel through a tissue, what is
the thickness of the tissue?
DISTANCE
•
•
•
•
Speed = distance
A 2.4 km
B 2.4 m
C 23 cm
D 24 mm
time
1600m/s = distance
1.5 x 10-5 s
.024m = distance
The table above shows experimental data collected when
four cars moved along a straight-line path. According to
these data, which car moved with a constant
You can immediately
acceleration of 2 m/s2 ?
A
B
C
D
Car Q
Car R
Car S
Car T
a =final velocity – initial velocity eliminate Q & R…WHY?
∆T
A(carS) = 4m/s-2m/s = 2m/s
2s-1s
1s
Use this method to check car S & car T.
Newton’s
Law of Motion
st
1
A body in motion will remain in motion.
A body at rest will remain at rest.
UNLESS there is a force acting on that object.
Newton’s 2nd Law of Motion
Force = mass x acceleration
Newton’s 3rd Law of Motion
For every action (force) there is an
equal and opposite reaction (force).
Friction
A force that acts in a
direction opposite to the
motion of two surfaces in
contact with each other.
MOMENTUM
• The effect of motion is momentum.
• Momentum = Mass x Velocity
Work
• Work: amount of energy
transferred by a force
• 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 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
SIMPLE MACHINES
make WORK easier
3 Classes of LEVERS
(Resistance)
The human bicep muscle is a classic
example of a third class lever. Similar
analogies can be drawn from almost all
joints in the human body.
•
% Efficiency
• NO MACHINE IS 100%
efficient.
• Energy is lost as HEAT!!!
%efficiency = work output X 100
work input
WAVES
Velocity of a wave = frequency x wavelength
(m/s)
(Hz)
ν
=ƒx
(m)
ENERGY = mass x (speed of light)2
KINETIC ENERGY- energy of motion
KE= ½ (mass x velocity)2
GRAVITATIONAL POTENTIAL ENERGY
PE= mass x acceleration due x height
to gravity
Electricity – flow of
electrical charge
Current = Voltage / Resistance
Electrical Power = Voltage x Current
Electrical energy = power x time
Convection, Conduction, and
Radiation
• Convection- Heat transfer by the mass
movement of molecules
•
Convection, Conduction, and
Radiation
• Conduction- Heat transfer by the collision
of molecules that are in contact
Convection, Conduction, and
Radiation
• Radiation- Heat transfer with no physical
contact
Convection, Conduction, and
Radiation
.
PRACTICE WITH YOUR
FORMULA CHART
• EVERY FORMULA YOU NEED IS ON
THE CHART.
• You won’t ALWAYS use all the
numbers given.
• Eliminate bad answers.
• ALWAYS use your calculator!!!!
Density of an object is
1.25 g/ml at 20°C and the
mass is 4 g, what is the
volume?
An object falling
from the sky traveled
4000 m in 8
seconds, what is the
speed of the
object?
A car accelerates
from 0 m/s to 100
m/s in 5 seconds.
What is the
acceleration of the
car?
A 0.75 kg ball is thrown
with a velocity of 40 m/s,
what is the
momentum of the ball?
A 25 kg rock is
increasing in velocity
from 0 m/s to 50 m/s
in 10
seconds. What is
the rock’s force?
If a box is
moved 5 m with
a force of 100 N,
how much work
is done?
How much power
is the result of
completing 5000 J of
work in 30
seconds?
What is the %
efficiency of a
machine if the work
output is 40 J and
the
work input is 50 J?
What is the kinetic
energy of a 100 kg
object traveling a 5
m/s?
What is the
potential energy of a
50 kg rock sitting on
top of a 75 m
cliff?
What is the velocity
of a wave with a
frequency of 1000 hz
and a
wavelength
of 0.00000045 m?