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Chapter 1 Physical Science South Ark online

Terms in this set (61)

Erathsthenes
measurements to show size of earth
what is distance between the earth and the sun
twice the distance to the moon
Aristotle logic
forces are not necessary to keep an object moving
Aristotle classified motion into 2 kinds:
natural (straight up and down) and violent (motion resulting from an external push or pull)
Galileo logic
experimentation
Galileo concept of inertia
in the absence of a force , objects set in motion continue moving indefinitely
What refuted aristotle's teaching?
Galileo leaning tower of pisa
What did Galileo leaning tower of pisa show?
dropped objects fall to the ground at the same time when air resistance is negligible
Do light and heave objects gain same amount of speed when falling?
yes
Galileo rolling ball experiment showed what?
balls rolling down inclined planes and then up others tend to roll back up to their original height
Inertia
property of things to resist change
The use of inclined planes for Galileo's experiments helped him to
discover the property called inertia
Mass
a measure of how much inertia an object has
quantity/quality of matter in an object
What does weight depend on?
gravity
weight
the amount of gravitational pull on an object
unit of mass
Kg
Unit of weight
Newton
What is the difference between Mass and Volume?
Mass is how much matter an object contains, Volume is how much space an object occupies
The concept of inertia mostly involves
mass
What does weight depend on?
location
Mass is same or more on earth than it is on the moon?
mass is same on earth as the moon
Weight is greater on earth than it is the moon?
weight is greater on earth
Equation for density
Density=mass/density
density
measure of how much mass occupies a given space
unit of measurement for density
g/cm3 or kg/cm3
the density of 1 kg of iron is : the same on the moon, less on the moon or greater on the moon
same on the moon
Force
simply a push or a pull
net force
The combination of all forces acting on an object
A cart is pushed to the right with a force of 15 N while being pulled to the left with a force of 20 N. The net force on the cart is
5 N to the left
What is the net force of a crate sliding at an unchanging speed when pushed with a steady force of 75N?
zero
equilibrium rule
the vector sum of forces acting on a non-accelerating object or system of objects equals zero
What does the equilibrium rule apply to?
objects in motion and objects at rest
Support Force
The force that supports an object against gravity
When you stand on two bathroom scales with one foot on each scale and weight evenly distributed, each scale will read what?
half your weight
Equilibrium
an object that moves constant velocity
when two or more forces cancel to zero on a moving object, then the object is in what?
equilibrium
When is a bowling ball in equilibrium?
it is at rest and moves steadily in a straight-line path
friction
The resistive force that opposes the motion or attempted motion of an object either past another object with which it is in contact or through a fluid.
friction force is opposite in direction to the _______
velocity
The force of friction can occur:
A. with sliding objects
B. in water
C. in air
D. All of the above
D. all of the above
When Nellie pushes a crate across a factory floor at constant speed, the force of friction between the crate and the floor is
equal and opposite to Nellie's push (same as the pushing force)
When Nellie pushes a crate across a factory floor at an increasing speed, the amount of friction between the crate and the floor is
less than Nellie's push
Speed
The distance an object travels per unit of time
Equation for speed
speed = distance/time
Equation for average speed
total distance covered/travel time
Instantaneous speed
speed at any instant of time
something that accelerates undergoes a change in ______________
velocity per unit of time
The average speed in driving 30km in 1 hour is the same average speed as driving
60 km in two hours
A hungry bee sees a flower in a 5-m/s breeze. How fast and in what direction should the bee fly in order to hover above the flower?
it should fly toward the flower, then at 5 m/s into the breeze
Acceleration
The rate at which velocity changes with time; the change in velocity may be in magnitude, or direction, or both.n (rate at which you change in time)
formula for acceleration
acceleration = change of velocity/time
difference in velocity and acceleration
velocity: change in your position in a time interval
acceleration: change in velocity in a time interval
An automobile cannot maintain a constant speed when:
accelerating,
rounding a curve,
both
none of the above
both---accelerating and rounding a curve
acceleration and velocity are actually
rates, but for different quantities
What is acceleration of an object in free fall at earth's surface?
10m/s2
free fall
when the only force acting on a falling object is gravity
During each second of free fall, the speed of an object
increases by the same amount
If a falling object gains 10 m/s each second it falls, its acceleration is
10 m/s per second
A free-falling object has a speed of 30 m/s at one instant. Exactly one second later its speed will be
more than 35 m/s
The distance fallen by a free-falling body
increases each second when falling
6 seconds after starting from rest a free falling baseball has a speed of _______
60 m/s
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