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Chapter 8 Sciece Test
These are the 77 Questions and Answers to our CH 8 Test
77
Science
Not Applicable
03/22/2005

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Term
You have 2 photos of a person walking. 1 shows the person at the corner of 3rd and main streets, the other shows the person at the corner of 10th and main streets. there are lampposts at every corner in this town, and the first pic shows it to be 10:32 ex
Definition
2 mi/hr
Term
a tube of air contains a feather and a coin. both objects are dropped at the same time. the soin falls faster than the feather. however, when the air is removed from the tube to create a vacuum, both the feather and the coin reach the bottom at the same t
Definition
without the force of gravity, all objects have the same weight, and therefor fall at the same speed
Term
using the terms acceleration, velocity, speed and inertia, explain why wearing a seat belt saves lives. also explain why shoulder belts and lap belts used together are more effective than lap belts alone.
Definition
when you accelerate, you're forced backwards, the speed of the car increases, as does your inertia. when you stop, your body wants to go forward, and that is when your seatbelt holds you back from flying out the front windshield. just using a lap belt, your velocity would make the top part of your body fly forward is you abrubtly stopped.
Term
because the speed of an object can change from one instant to the next, dividing the distance covered by the time of travel gives
Definition
speed
Term
when an object is seen moving against a statinoary background, what is the stationary background called?
Definition
reference frame
Term
if an object traveling in one direction has a positive velocity, what kind of velocity would the same object traveling in the oppposie direction have?
Definition
negative
Term
which has greater momentum, a small pick-up truck traveling 55 mi/hr or a full-sized bus traveling at the same speed?
Definition
the full-sized bus
Term
a large truck loaded with scrap steel weighs 14 tons and is traveliong north on the interstate heading fro Chicago. It has been averaging 48 mi/hr for the journey and has traveled over 1450 miles so far. It has just stopped to refuel. what is its current
Definition
0 tons x mi/hr
Term
If two objects with different masses and traveleing with different velocities collide, what law allows you to predict the motion of the objects after the collision.
Definition
Newton's 3rd law
Term
A small sports car traveling south collides with a heacy truck traveling north. both vehicles are going at the same speed. which will be moved off course by collision and in which direction?
Definition
the small sports car, north
Term
If two vehicles collide, name at least one outside force thay will come into effect immediately after the impact and cause the objects to eventually come to a stop.
Definition
friction
Term
define acceleration.
Definition
change in velocity divided by the time interval in which the change occurred.
Term
in your own words, explain the similarities and differences between velocity and acceleration.
Definition
velocity describes speed and direction whereas acceleration describes the change in velocity divided by the time it took for the change to happen. both involve speed and direction
Term
explain why a cyclist accelerates when turning a corner even if her speed doesn't change.
Definition
because she is changing her direction, which is a change in velocity, which is acceleration
Term
during a race, a sprinter increases from 5.0 m/s to 7.5 m/s over a period of 1.25 s. what is the sprionter's average acceleration during this period?
Definition
2 m/s^2
Term
two archers shoot identical arrows at a target from exactly opposite directions. use your knowledge of net forces to describe the movement of the target.
Definition
the target won't move because the forces cancel each other out.
Term
Distinguish between balanced forces and unbalanced forces.
Definition
balanced forces combine to produce a net force equal to zero whereas unbalanced forces combine to produce a net nonzero force
Term
what will the result be if two equal forces act on a single object from different directions that are not exactly opposite?
Definition
it will move in one direction.
Term
why is it easier to push a crate over a smooth concrete sidewalk than over grass?
Definition
because the grass has more friction which takes more force
Term
you are pushing a heavy crate across a cement floor when you hit a section of flooring covered with smooth stell plates. suddenly it is somewhat easier to push the crate. why?
Definition
the plates have less friction than the floor
Term
list two situations in which friction is helpful or necessary.
Definition
1. hitting the brakes of a car
2. a car parked on a hill
Term
state newton's first law.
Definition
an object at rest remains at rest and an object in motion maintains its velocity unless it experieces and unbalanced force.
Term
state newton's second law.
Definition
the unbalanced force acting on an object equals the object's mass times its acceleration
Term
express the following as an equation: One newton is the force that can give an object with a mass of 1 kg an acceleration of 1 m/s^2.
Definition
1 N = 1 kg x 1 m/s^2
Term
rearrange the equation for newton's second law of motion to define acceleration in terms of force and mass.
Definition
a = F/m
Term
what is free fall?
Definition
the motion of a body when only the force of gravity is acting on it
Term
where is the free fall acceleratino of an object under earth's gravity directed?
Definition
toward the center of the earth
Term
what is the value for the acceleration of objects in free fall near earth?
Definition
9.8 m/s^2
Term
in the abscence of air resistance, how would the acceleration of a 1.5 kg book and the acceleration of a 15 kg rock differ if the objects were dropped from the same height
Definition
the rock would hit the ground first and then the book
Term
does the direction of an object falling toward differ from the direction of an object falling through water on earth? why or why not?
Definition
no, because they both fall toward the center of the earth
Term
what is the difference between mass and weight?
Definition
mass is a measure of the amount of matter in an oject whereas weight is the gravitational force an objecty experiences due to its mass
Term
how does gravity influence the shapes of living things?
Definition
depending on the location of an animal/object, that animal will either be a vertabrate or an invertabrate and that object's structure will be sturdier/weaker
Term
define terminal velocity.
Definition
the maximum velocity reached by a falling object that occurs when the resistance of the medium is equal to the force due to gravity
Term
how would the terminal velocity of an object falling toward earth differ from the terminal velocity of the same object falling through water and why?
Definition
the terminal velocity of an object falling toward earth would be greater than that of the same object falling through water because water has more resistance than air and would slow the object down more
Term
why does it require less fuel to accelerate a rocket in outer space than required in earth's atmosphere?
Definition
because air is more dense on earth
Term
what is the velocity of an object called when gravitational forces and air resistance equalize on an object that is falling toward earth and the object stops accelerating?
Definition
terminal velocity
Term
when an object covers equal distance in equal amounts of time, it is moving at a(n) ____ speed.
Definition
constant
Term
velocity describes both speed and ____
Definition
direction
Term
mass times velocity equals ____
Definition
momentum
Term
according to newton's second law of motion, force is the product of ____ and ____
Definition
mass, acceleration
Term
what is the approximate terminal velocity of a sky diver before the parachute opens?
Definition
d) 320 km/h
Term
which of the following does nto indicate velocity?
Definition
d) 28 miles from Los Angeles to Catalina Island
Term
The difference between speed and velocity is that velocity includes
Definition
a) direction
Term
which of the following is not a factor in calculating momentum?
Definition
c) acceleration
Term
if you divide momentum by velocity, the result is the value of the object's
Definition
a) mass
Term
whenever an object is standing still, the value(s) that is/are always zero is/are
Definition
d) all lof the above
Term
a 10.0 kg dog chasing a rabbit north at 6.0 m/s has a momentum of
Definition
b) 60.0 kg•m/s north
Term
if you are given the mass of an object in punds, the time in seconds, and the distance in feet, what must you do before you can calculate the momentum in SI units?
Definition
e) only a and b above
Term
acceleration is defined as the change in velocity divided by
Definition
c) time
Term
the SI unit for acceleration is
Definition
c) m/s^2
Term
on a velocity-time graph, a line with a negative slope indicates that the object is
Definition
b) slowing down
Term
when the velocity of an object changes, it is acted upon by a(n)
Definition
a) force
Term
the combinations of all the forces acting on an object is called the
Definition
d) net force
Term
If the net force acting on a stationary object is zero, then the object will
Definition
b) remain at rest
Term
If the net force on an object is zero then the object has
Definition
c) balanced forces
Term
a tug-of-war that results in one team pulling the other across the line is an example of
Definition
d) unbalanced forces
Term
which of the following best illustrates balancede forces?
Definition
b) a stretched rubber band being held between two hands
Term
frictin is defined as
Definition
a) force that opposes motion between two surfaced that are touching
Term
a force is continuously applied to an object, causing it to accelerate. after a period of time, however, the object stops accelerating. what conclusions can be drawn?
Definition
c) the object is experiencing some kind of friction
Term
which of the following situations best demonstrates the effects of friction?
Definition
d) two trucks colliding
Term
an airplane is flying at 635 miloes per hour at an altitude of 35 000 feet. it is currently over Kansas and is approximately 16 minutes ahead of its scheduled arrival time. what is its velocity?
Definition
d) this cannot be determined without further information about its direction.
Term
which of the following statements is true?
Definition
a) frictional forces are greatest when both surfaces are rough.
Term
weight is best described as
Definition
c) the downward force exerted on objects due to gravity
Term
when objects are moved further apart from each other, the force of gravity
Definition
c) decreases
Term
of the following, the greatest gravitational force would occur between
Definition
d) the moon and Earth
Term
the law that states that every object maintains constant velocity unless acted on by an unbalanced force
Definition
a) newton's first law of motion
Term
the law that states that for every action force there is an equal and opposite reaction force is
Definition
c) newton's third law of motion
Term
the law that states that the unbalanced force acting on an object equals the object's mass times its acceleration is
Definition
b) newton's second law of motion
Term
the SI unit of force, named for the scientist who described the relationship between motion and force, is called the
Definition
a) newton
Term
one pound is equal to how many newtons?
Definition
a) 4.448 N
Term
which of the following units is used to measure acceleration in free fall?
Definition
c) m/s^2
Term
which of the following equations is correct?
Definition
a) w = mg
Term
which of the following is true?
Definition
d) all of the above
Term
when air resistance balances the weight of an object that is following, the velocity
Definition
b) remains constant
Term
the distance traveled by an object divided by the time it takes to travel that distance is called
Definition
b) average speed
Term
in order to determine speed, you must know
Definition
c) both a and b
Term
what is the speed of an object at rest?
Definition
b) 0 km/h
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