99 terms

Conceptual Physics: Forces and Newton's Laws Practice Questions

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false
a force is required to keep an object moving in a given direction (T/F)
false
an upward moving object must be experiencing (or at least usually does experience) an upward force (T/F)
false
a rightward moving object must be experiencing (or at least usually does experience) a rightward force (T/F)
false
a ball is moving upwards and rightwards toward its peak. The ball experiences a force that is directed upwards and rightwards (T/F)
false
if a person throws a ball with his hand, then the force of the hand upon the ball is experienced by the ball for at least a little while after the ball leaves the hand (T/F)
false
a cannonball is shot from a cannon at a very high speed. The force of the explosion will be experienced by the cannonball for several seconds (or at least for a little while) (T/F)
false
if an object is at rest, then there are no forces acting upon the object (T/F)
false
objects do NOT weigh anything when placed in a vacuum (T/F)
false
all objects weigh the same amount when placed in a vacuum, regardless of their mass (T/F)
true
an object weighs less on the moon then it does on the Earth (T/F)
true
the mass of an object on the moon is the same as its mass on the Earth (T/F)
false
a high speed object (say, moving at 200 mi/hr) will weigh less than the same object when at rest (T/F)
false
a high speed object (say, moving at 200 mi/hr) will possess measurably more mass than the same object when at rest (T/F)
false
weight is measured ion pounds; mass is measured in Newtons (T/F)
true
a free falling object still has weight (T/F)
false
weight is the result of air pressure exerted on an object (T/F)
a force can cause a resting object to move
what can a force do to a resting object?
by changing the object's speed or direction
how can a force accelerate a moving object?
a spring scale
what are forces measured on?
a force that causes a 1-kilogram mass to accelerate at a rate of 1 meter per second sech second
newton
the overall force acting on an object after all the forces are combined
net force
the net force is zero and there is no change in the object's motion
what happens when the forces of an object are balanced?
the object accelerates
what happens to an object when an unbalanced force acts on it?
a force that results when the net force acting on an object is not equal to zero
unbalanced force
produce an unbalanced force
forces acting in opposite directions can also combine to...
the size of the larger force minus the size of the smaller force
what does the net force equal to?
a force that opposes the motion of objects that touch as they move past each other
friction
the friction force that acts on objects that are not moving
static friction
the direction opposite to that of the applied force
which direction does static friction always act in?
taking a step
example of static friction
a force that opposes the direction of motion of an object as it slides over a surface
sliding friction
less force is needed to keep an object moving than to start it moving
because sliding friction is less than static friction....
pushing a pot across a patio
example of sliding friction
the friction force that acts on rolling objects
rolling friction
round object rolls across a flat floor
example of rolling friction
because they replace sliding friction with rolling friction
why do ball bearings reduce friction in machines?
opposes the motion of an object through a fluid
fluid friction
acts on a submarine moving through water or a plane in the air
examples of fluid friction
fluid friction acting on an object moving through the air
air resistance
a force that acts between any two masses
gravity
a force of attraction on every other object that is near Earth
what does Earth's gravitational force exert?
downward
does Earth's gravity act downward or upward on the center of the Earth?
upward, downward
an ____ force usually balances out the ____ force of gravity
opposite, reduces
air resistance acts in the direction ____ to the motion and ____ acceleration
they accelerate, gain more speed, and gain more air resistance
what three things happen when objects fall to the ground?
the upward force of air resistance becomes equal to the downward force of gravity, making them balanced
what happens if an object falls for a long time?
the constant velocity of a falling object when the force of air resistance equals the force of gravity
terminal velocity
the motion of a falling object after it is given an initial forward velocity
projectile motion
force is required to keep an object moving at a constant speed
what did Aristotle incorrectly propose?
moving objects not subjected to friction or any other force would continue to move indefinitely
what did Galileo conclude?
unless an unbalanced force acts, an object at rest remains at rest, and an object in motion remains in motion with the same speed and direction
Newton's first law of motion
it does not
does the state of motion of an object change if net force acting on the object is zero?
the tendency of an object to resist a change in motion
inertia
velocity
an unbalanced force causes an object's ____ to change
the measure of inertia of an object and depends on the amount of matter the object contains
mass
the acceleration of an object is equal to the net force acting on it divided by the object's mass
Newton's second law of motion
acceleration = net force/mass
equation regarding the second law of motion
a deceleration that reduces the speed
when a net force acts in the direction opposite to the object's motion, the force produces....
the force of gravity acting on an object
weight
mass x acceleration due to gravity
equation of weight
newtons
unit of force/weight
meters per second per second
unit of acceleration/gravity
kilograms
unit of mass
inertia, force, gravity
mass is a measure of the ____ of an object; weight is a measure of the ____ of ____ acting on an object
whenever one object exerts a force on the second object, the second object exerts an equal yet opposite force on the first object
Newton's third law of motion
no
do all action and reaction forces produce motion?
no
do all action and reaction forces act on the same object?
when the equal and opposite forces act on the same object
when do action and reaction forces result in a net force of zero?
the product of an object's mass and its velocity
momentum
if the product of its mass and velocity is large
when does an object have a large momentum?
zero
what is the momentum for any object at rest?
the momentum does not increase or decrease
what does a conservation of motion mean?
if no net force acts on a system, then the total momentum of the system does not change
the law of conversion of momentum
the loss of momentum of one object equals the gain in momentum of another object
what happens in a closed system?
associated with charged particles
electromagnetic force
electric forces and magnetic forces
what are the only two forces that can both attract and repel?
charged objects or particles
what do electric forces act between?
attract
objects with opposite charges ____ one another
repel
objects with like charges ____ one another
certain metals, on the poles of magnets, and on moving charges
what do magnetic forces act on?
north and south
what two poles on magnets attract each other?
the electric force of repulsion that acts among the protons in the nucleus
what does the strong nuclear force overcome?
a powerful force of attraction that acts only on the neutrons and protons in the nucleus, holding them together
strong nuclear force
an attractive force that acts only over a short range
weak nuclear force
an attractive force that acts between any two masses
gravitational force
every object in the universe attracts every other object
what does Newton's law of universal gravitation state?
a center-directed force that continuously changes the direction of an object to make it move in a circle
centripetal force
pulls the moon into a nearly circular orbit around Earth
what does the center-directed force of Earth's gravity do?
the law of gravity and the three laws of motion
what did Newton discover?
no
does gravity have to have a force balancing it out?
velocity
an object in motion will stay in motion at a constant _____
pictorial representation of all forces acting on a object
free body diagram
accelerate
if an object does not have a force, it cannot ______
proportionally
if you increase the force, you increase the acceleration ______
mass
acceleration is proportional to one over the _____
small, constant
large mass equals ____ acceleration if the force is kept _____
small, constant
large acceleration equals ____ mass if the force is kept _____
directly, inversely
acceleration is ____ proportional to force and ____ proportional to mass
quadruples
doubling the mass and doubling the acceleration _____ the force