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57 terms

physics midterm

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the symbol mm represents
millimeter
the SI base unit to measure mass is the
kilogram
if some measurements agree closely to with each other but differ widely from the actual value, these measurements are
precise
five darts strike near the center target. the dart thrower is
accurate
the greek letter delta ▲ indicates a ____
the greek letter sigma Σ indicates _____
difference; change
what are the basic SI units
m kg s
what is the speed of an object at rest
0
a vector makes an angle with the horizontal. the vertical and horizontal components will be the same if the angle is
45°
a golf ball is hit at an angle above the horizontal. what is the acceleration of the golf ball at the highest point in its trajectory? [neglect friction]
less than or equal to 9.8 m/s^2
a ball is thrown from a high window. how far would you describe the acceleration of the ball during its fall?
falls slowly then gradually speeds up
a ball is thrown horizontally from the top of a building with an initial velocity of 15m/p/s at the same instant, a second ball is dropped from the top of the building. the two balls have the same
acceleration and initial vertical velocity
a projectile is launched horizontally from a cliff and eventually hits the ground below. assume the air resistance is negligible. how do the downward and horizontal components of the projectile's velocity behave during the motion
downward- increases horizontal- same
the SI unit for time is a
second
acceleration due to gravity is also called
free fall acceleration
the baseball catcher throws a ball vertically upward and catches it in the same spot as it returns to the mitt. at what point in the balls path does it experience zero velocity and nonzero acceleration at the same time
at the top of its trajectory
what can be said about the displacement of objects of different masses falling with no air resistance
similar displacements and equal acceleration
how does the velocity of objects that are falling toward earth change as they fall
it becomes greater
which would hit the ground first if dropped from the same height in a vacuum a feather or a metal bolt in the absence of air resistance
neither
which would fall with greater acceleration in a vacuum, a leaf or a stone
neither same acceleration
what is a physical quantity that has a magnitude but no direction
scalar
what is a physical quantity that has both magnitude and direction
vector
what is an example of a vector quantity? what is an example of a scalar quantity?
velocity; temp vol mass
a lightning bug flies at a velocity of 0.25m.s due east toward another lightning bug seen off in the distance. a light easterly breeze blows on the bug at a velocity of 0.25m/s. what is the resultant velocity of the lightning bug
0m/s
what is the motion of objects in two dimensions under the influence of gravity
projectile motion
what is an example of projectile motion? what is not?
a baseball being hit; a jet lifting off a runway
what increases and what stays the same as an object falls freely in a vacuum
velocity increases acceleration stays the same
what is the path of a projectile
a parabola
a basketball player jumps to make a shot. once her feet are off the floor the jumpers acceleration is
-9.8m/s^2
the horizontal component of a projectiles velocity is independent of
the vertical component
a ball thrown through the air will never go as far as physics ideally would predict because of
air friction
suppose you throw a ball straight upward. ignore air resistance. how would you describe the ball acceleration and velocity from the instant the ball leaves your hand until it reaches its highest peak
acceleration is constant velocity decreases
th velocity of an object in free fall on the moon depends on
acceleration of gravity only
what does a force do
starts stops or changes the state of a moving object
what type of forces arise from direct physical contact between two objects
contact force
what type of force exist between objects even in the absence of direct physical contact
field force
what is the tendency of an object to maintain its state of motion
inertia
what is an example of a contact force? what is an example of a field force?
cf- friction normal tension ff- magnetic gravitational electrical
a hammer drives a nail into a piece of wood. identify an action-reaction pair
hammer hits nail nail hits hammer
a free-body diagram of a ball in free fall in the presence of air resistance would show
up Fair down Fn
a car goes forward along a level road at constant velocity. the additional force needed to bring the car into equilibrium is
0
a leaf falls from a tree and lands on a sidewalk. identify an action-reaction pair
leaf pushes on sidewalk sidewalk pushes on leaf
the statement by newton that for every action there is an equal but opposite reaction is which of his laws of motion
third
what are simultaneous equal but opposite forces resulting from the interaction of two objects
action-reaction pairs
the magnitude of the force of gravity acting on an object is called
weight
a box is pushing toward the right across a classroom floor. the force of friction on the box is directed toward the
left
a man is pushing a baby stroller. compared to the magnitude of the force exerted on the stroller by the man, the magnitude of the force exerted on the man by the stroller is
the same
compared to the force needed to start sliding a crate across a rough level floor the force needed to keep it sliding once it is moving is
less
a change in the force of gravity acting on an object will affect the objects
weight
what measures the ability of a force to rotate or accelerate an object around an axis
torque
concerning the amount of torque produced what is true about the position of the force in relation to the axis of rotation
the closer to the axis the more force exerted
the centripetal force is always directed ___________ in circular motion
towards the center
where should a force be applied on a lever arm to produce the most torque
farthest from the axis of rotation
if you want to open a swinging door with the least amount of force where should you push on the door
farthest away from the hinges
if you cannot exert enough force to loosen a bolt with a wrench what should you do
use a longer wrench
the force that seems to cause a rotating object to move away from the center of rotation is a result of the
inertia of object
if the distance between earth and the moon were to increase to twice the present distance the gravitational force between the objects would be _____ the force at the present distance
1/4
which has a greater linear speed: a horse near the outside of the rail of a merry-go-round or a horse near the inside rail? which has a greater angular speed?
outside; neither- same speed