Transcript File

STUDY ISLAND MCAS REVIEW
PHYSICAL SCIENCE
Assignment #8
Motions of Objects,
Heat Energy
What is MOTION?
An object is in motion if its position changes relative to a
reference point (a non-moving object). The observed
motion changes when the reference point changes.
DESCRIBING MOTION
Do you remember these words?
ACCELERATION is the
Speed
rate of change in velocity
VELOCITY is the
– that means EITHER a
speed of an object
Velocity
change in speed OR a
in a given direction
change in direction per
unit of time.
Acceleration
SPEED is a rate – how much
distance is covered per unit of time
Speed = distance ÷ time
The car is traveling at 100 miles per
hour.
It is usually calculated as an
AVERAGE speed for a trip = TOTAL
distance ÷ TOTAL time
Acceleration = (Final
velocity – Initial velocity) ÷
time
C. Average
Speed = total
distance ÷ total
time: 3m ÷ 6s =
0.5m/s
An escalator at a shopping mall is
10 m long and moves at a
constant speed of 0.5 m/s. If
Jose steps onto the escalator at
the bottom while it is moving, how
long will it take him to travel the
10m?
A. 5 s
B. 10 s
C. 15 s
D. 20 s
Graphing Motion
On a
DISTANCE/TIME
graph, constant
speed or velocity
is a straight line.
A STEEPER line
means a faster
speed; a LESS
steep line means a
slower speed. A
line that is curved
upward like the
green one shows
ACCELERATION,
increasing speed.
D. Bicyclist U as his
motion is the only
one with a straight
line.
The force of GRAVITY
All objects in the universe exert a
gravitational pull on every other
object. Objects with MORE MASS
have MORE GRAVITY. Objects
that are closer exert more
gravitational force as well.
Earth is so much more MASSIVE
than any other object on earth that
its gravitational pull is what we
observe when objects fall.
Do you remember the difference
between mass and weight?
MASS is a measure of the amount of matter
in an object and doesn’t change from
place to place in the universe.
WEIGHT is the measurement of the
gravitational pull on an object, so it will
change if the force of gravity changes.
Newton’s Laws of Motion
1st Law: INERTIA – an object at rest stays at rest,
or an object moving at constant speed and
direction stays moving unless an unbalanced
force acts on it to change its motion.
2nd Law: F=ma – force = mass x acceleration. If
you throw a ball harder (more force), it will
accelerate faster and go farther.
3rd Law: Action – Reaction. One object exerts a
force on a 2nd object (action), and the 2nd exerts
an equal and opposite force back on the 1st
(reaction).
Force Diagrams – show all the
forces acting on an object
GRAVITY
AIR RESISTANCE
(FRICTION/DRAG)
THRUST
LIFT
HEAT energy, also called
THERMAL energy is an example of
KINETIC energy – do you
remember the difference between
POTENTIAL and KINETIC
energy???
• Potential energy is stored energy or
energy of position, while KINETIC energy
is energy of motion – the vibrating motion
of molecules in a substance.
TEMPERATURE is the average
kinetic energy of all the molecules
in a substance, where HEAT is the
total kinetic energy.
Temp =
90°C
Temp =
90°C
Mass
= 50g
Mass =
500g
The cup on the left has the SAME TEMPERATURE as the pan on
the right, but the amount of HEAT on the left is LESS as there are
fewer molecules of water.
Heat TRANSFER is a one-way road!
Warmer things always
transfer their heat to cooler
things. Cold things DO NOT
transfer their coldness – they
GAIN heat from something
warmer, while the warm
object loses heat.
Heat is transferred by:
CONDUCTION
By touch – one
particle
bumps into
or touches
another
CONVECTION
Heat RISES as
density is
lower, and
colder
substances
sink
OR…
RADIATION
Heat travels
across space
in waves
INSULATORS help PREVENT or
SLOW heat transfer – like insulation
in your home, a thermos or a cooler