Physics Final
an object with a momentum of inertia of 10 kgm^2 and angular velocity of 5RPM will have an angular momentum of
50 kgm^2/s
if an object is in stable equilibrium, any displacement will
raise its center of gravity
An object placed exactly halfway between Earth and moon will fall towards
Earth
T/F: Objects in a rotating reference frame seem to experience an outwardly directed centrifugal force.
True
T/F: Objects of the same shape but different sizes accelerate equally when rolled down an incline.
True
T/F: The gravitational force of the earth on an object decreases as the object moves farther from the earth.
True
the center of gravity on your body is located
at different places depending on body orientation
The rotational inertia of an object is greater when most of the mass is located
away from the rotational axis
Why did newton think there was a force acting on the moon?
because the moon moves in a curved path
As a satellite is moving in orbit around earth, the sum of the kinetic energy and potential energy everywhere is
constant
The speed of a satellite in circular orbit is
constant
for an object traveling in a circular path, its angular momentum doubles when its linear speed
doubles and its radius remains the same, remains the same and its radius doubles, and its radius remains the same and its mass doubles
Newton reasoned that the gravitational attracted between the earth and the moon must be
inversely proportional to the square of the distance between them
Newton hypothesized that the moon
is a projectile, is actually attracted to the earth, and has tangential velocity that prevents it from falling into the earth
when a stable object is made to topple over, its center of gravity
is at first raised
Which has greater ANGULAR speed, a horse near the outside rail of a merry go round or a horse near the inside rail?
neither
why do high jumpers arch their bodies into a U shape when passing over the bar?
they do this to alter the location of their center of gravity
what are the un its of power
watts, horsepower, joules per second
ordinarily when you stand with your back and heels to a wall, you cannot bend over and touch your toes without toppling over. why?
you cannot balance while touching your toes in this situation because your center of gravity extends beyond your support base.
a medicine ball has a mass of 5 kg and is thrown with a speed of 2 m/s. what is the kinetic energy?
10 J
a weight lifter presses a 400 N weight 0.5 m over his head in 2 seconds. what is the power of the weight lifter?
100 watts
an object weighing 75 N is dropped from the top of a building and falls a distance of 28 m to the ground. how much work does gravity do on the object from the time it is dropped to the time it hits the ground?
2100 J
a man pushes a crate along a factory floor by exerting a force of 55 N. if the crate moves a distance of 4.0m, how much work does the man perform?
220 J
what is the gravitational potential energy of a 55 kg box that is 8.0 m above the ground?
4300 J
an object has a kinetic energy of 810 J after falling a certain distance, if the mass of the object is 20 kg, what is the speed of the object at this time?
9 m/s
moment of inertia
how the mass of an object is distributed about a rotational axis
An ice skater is spinning fast with her arms tight against her body. When she extends her arms, which of the following statements are NOT true? A. She increases her momentum of inertia B. She decreases her angular velocity C. her momentum of inertia remains constant D. her total angular momentum will remain constant E. she will spin slower
C
T/F: Any object with a great rotational inertia will roll down an incline more quickly than one with a small rotational inertia.
False
T/F: Because the earth and moon are gravitationally attracted toward each other, they will collide soon.
False
T/F: Rotational Inertia depends on the force of gravity.
False
T/F: Rotational motion is always constant.
False
T/F: When a space station increases its rotational acceleration, the occupants feel less simulated gravity.
False
T/F: because the earth is "falling" around the sun, it will eventually crash into it.
False
T/F: centrifugal force is part of an interaction, therefor it is considered a real force in simulated gravity situations.
False
What is the direction of the force that acts on cloths in the spin cycle of a washing machine?
Inward
What remains constant for a satellite in an elliptical orbit?
Its total energy
Units for momentum of inertia
Kg * m^2
Symbol for angular momentum
L
Momentum of inertia of a ring about an axis equation
M*R^2
T/F: According to the Law of Inertia, rotating objects tend to keep rotating.
True
A ladybug resets on the bottom of a tin can that is being whirled in a horizontal circle at the end of a string. What exerts the force that holds this ladybug in a circle?
The can
T/F: Any moving object has momentum.
True
Which has a greater LINEAR speed, a horse near the outside rail of a merry go round or a horse near the inside of the rail?
The outside
A tin can whirled on the end of a string moves in a circle because...
There is a force on the can pulling it inward
the law of conservation of energy states that
energy can neither be created nor destroyed
an unsupported object will topple over when its center of gravity
extends beyond the support base
A bug on a turntable will make more turns per minute if it is located nearer to the center of the record
false
T/F: Newton's 1st Law does not apply to rotating objects
false
t/f: the center of mass of an object is always located inside the geometric bounds of an object
false
t/f: work and energy are always equal
false
Newton had the insight to see that the
force on the moon has the same nature as the force on an apple
if an object is in unstable equilibrium, any displacement will
lower its center of gravity
the center of gravity of an objet
may or may not lie inside the object
Gravity can be simulated for astronauts in outer space if their habitat
rotates
the center of gravity of an object can be located by
the intersection of vertical lines drawn from suspension points or balancing it above your finger
gravitational potential energy depends on
the mass, the height, and the acceleration due to gravity
The fastest moving planet in a solar system
the planet nearest to the sun
Angular momentum
the product of momentum of inertia and angular velocity
A period of a satellite
the time for a satellite to make one complete revolution around Earth
Any force that causes an object to move in a circular path is called a centripetal force
true
It is possible to rotate a very large cylindrical space habitat around its central axis at just the right speed so people inside the cylinder will experience a force that feels like gravity
true
The outside rim of a rotating turntable has a greater linear speed that parts closer to the axis
true
t/f: an unaided object will topple over when its center of gravity extends beyond its support base
true
when you whirl a can on the end of a string, the centripetal force on the can is actually the pull of the string on the can
true
a boy pushes on a parked car with a force of 200N. the car does not move. how much work does the boy do on the car?
zero
