Chapter 9 Practice Problems
What is the force of gravity on a 500-N woman standing on Earth's surface?
500 N
When you weigh yourself on a bathroom scale on a slight incline instead of a level surface, your weight reading on the scale will be
Less
Which is most responsible for Earth's ocean tides?
Moon
Wobbles in the path of Uranus led to the discovery of
Neptune
The concept of force is fundamental to
Newton's theory of gravitation.
All places on Earth would have high tides at the same instant if the
None of the following: Moon did not revolve, Moon did not rotate, Sun did not revolve, Sun did not rotate.
Two planets in space gravitationally attract each other. If both the masses and distances are doubled, the force between them is
None of the following: one-quarter, half as much, twice as much, four times as much.
One side of the Moon continually facing Earth is
Tidal lock
In comparison with other fundamental forces, the universal gravitational constant G indicates that gravity is
Very weak
If a block is set sliding on a huge imaginary frictionless plane in contact with Earth's surface, it will NOT sustain a constant speed because
a component of gravitational force parallel to the plane soon acts on it.
The universal gravitational constant G was first measured
after Newton's time
We do not observe tides in a community swimming pool because
all parts of it are practically the same distance from the Moon.
Rate this statement: No force due to Earth's gravity acts on astronauts inside the orbiting space station.
always false
Surrounding a magnet is a magnetic field. Surrounding an electron is an electric field. Surrounding Earth is
an alteration in space in which mass experiences a force, and a gravitational field.
Earth's gravitational field extends
both inside and outside Earth and throughout the entire universe.
To make a profit a buyer purchases metal by weight at one altitude and sells it at the same price per pound at another altitude. The supplier should
buy at a high altitude and sell at a low altitude
How far must one travel to escape Earth's gravitational field?
forget it; you can't travel far enough.
The force of Earth's gravity on a capsule in space increases as it comes closer. When the capsule moves to half its distance, the force toward Earth is then
four times greater
According to Newton, the greater the masses of interacting objects, the
greater the gravitational force between them
If the Moon were four times as massive but twice as far from Earth, high tides on Earth would be
lower
Each of us weighs a tiny bit less inside the ground floor of a skyscraper than we do on the ground away from the skyscraper because the
mass of the building above slightly attracts us upward.
The amount of gravitational force that acts on a space vehicle while in Earth orbit is
nearly as much as the vehicle's weight on Earth's surface.
The best time for digging clams (when the low tide is extra low) is during the time of the
new or full moon
If the Sun became twice as massive, your attraction to the Sun would double and your weight as measured on Earth would
not change
Tides caused mainly by the Moon occur in Earth's
oceans, interior and atmosphere
The main reason ocean tides exist is that Moon's pull is stronger
on water closer to it than on water farther away.
Which rocket would require more fuel?
one going from Earth to the Moon.
The force of Earth's gravity on a capsule in space will lessen as it moves farther away. If the capsule moves to twice its distance, the force toward Earth becomes
one-fourth
Half-way to the center of a planet of uniform density, your weight compared to that at the surface would be
one-half
According to Newton, when the distance between two interacting objects doubles, the gravitational force is
one-quarter
Suppose the Moon had twice the diameter but the same mass and same orbital distance from Earth. In that case, the high tides on Earth would be
practically the same
When a star collapses to form a black hole, its mass
remains the same
If you drop a stone into a hole drilled all the way to the other side of Earth (neglect the molten core), the stone will
speed up until it gets to Earth's center.
The factor most directly responsible for making a black hole invisible is its
surface escape velocity.
The difference between Newton's law as a proportion and an equation involves
the constant G
Planets wobble in their orbits due to
the gravitational attraction to other planets.
Which produces a greater tidal effect in your body, the Moon or a 1-kg melon held at arm's length above your head?
the melon
A black hole is
the remains of a giant star that has undergone gravitational collapse.
If the Sun collapsed to a black hole, Earth's gravitational attraction to it would be
the same
Tidal bulges on the Moon involve the concept of
torques
An asteroid exerts a 360-N gravitational force on a nearby spacecraft. The 360-N force on the spacecraft is directed
toward the asteroid
Tidal forces in general are the result of
unequal forces acting on different parts of a body
Inside a freely-falling elevator, you would have no
weight
Inside a freely-falling runaway elevator, your
weight is zero.
Passengers in a high-flying jumbo jet feel their normal weight in flight, while passengers in an orbiting space vehicle do not, because passengers in the space vehicle are
without support forces
When you step on a weighing scale at noon, Earth pulls you downward and the overhead Sun pulls you upward. The reason the Sun's pull doesn't decrease your weight at noon is because
you, the scale, and Earth are in free fall (in orbit) around the Sun
Half-way to the center of a completely hollow planet with a thin uniform shell, your weight would be
zero
During an eclipse of the Sun the high ocean tides on Earth are
extra high
Pluto is classified by as a
Dwarf planet
The origin of any microtides in the human body is most likely the
Earth
Which pulls on the oceans of Earth with a greater force?
Sun
If you jounce up and down on a bathroom scale, what varies on the scale reading is
The normal force
If Earth's radius somehow increased with no change in mass, your weight would
decrease
If Earth's mass decreased to one-half its original mass with no change in radius, then your weight would
decrease to half
On each given day and location, tides rise and fall at
different times
You can experience weight
in a rotating habitat in space, standing on Earth's surface, and in an accelerating elevator away from earth
The direction of a gravitational field is
in the same direction as gravitational attraction.
If the mass of Earth somehow increased with no change in radius, your weight would
increase also
As two objects moving toward each other due to gravity get closer, the acceleration of each
increases
Two objects move toward each other due to gravity. As the objects get closer and closer, the force between them
increases
When the distance between two stars decreases by one-third, the force between them
increases to nine times as much
If the Moon had twice as much mass and still orbits Earth at the same distance, ocean bulges on Earth would be
larger
You experience weightlessness
- in the absence of a supporting surface. - in a freely falling elevator. - momentarily when you step off a chair.
A weight watcher who normally weighs 400 N stands on top of a very tall ladder so she is one Earth radius above Earth's surface. How much is her weight there?
100 N
If the Moon were covered with water, tidal effects caused by Earth would find the Moon with
2 tidal bulges.
An asteroid exerts a 360-N gravitational force on a nearby spacecraft. If the spacecraft moves to a position three times as far from the center of the asteroid, the force will be
40 N
An outcome of universal gravitation is that
All of the following: planets aren't cubes with sharp corners, its discovery prompted other laws of nature, prediction and discovery of planets.
Your weight is the force
B) you exert against a supporting surface
If the Sun were twice as massive
Both of these: its pull on Earth would double, the pull of Earth on the Sun would double.
The identities of dark energy and dark matter are
Both of theses: unknown at this time, subjects of intense astronomical interest.
The planet Jupiter is about 300 times as massive as Earth, yet on its surface you would weigh only about 3 times as much because
C
If an object is placed exactly halfway between Earth and the Moon, it would fall toward the
Earth
There would be only one ocean tide per 24-hour day if the
None of the following: Earth and Moon were equally massive, Moon were more massive than Earth, Sun's influence on the tides were negligible, Moon's mass were small — only a few kilograms.
A very massive object A and a less massive object B move toward each other under the influence of gravity. Which force, if either, is greater?
both forces are the same
A hollow spherical planet is inhabited by people who live inside it, where the gravitational field is zero. When a very massive spaceship lands on the planet's surface, inhabitants find that the gravitational field inside the planet is
non-zero, directed toward the spaceship
For lunar tides to occur in the human body
parts of the body would have to be appreciably closer to the Moon than other parts.
The force of gravity acts on all apples on an apple tree. Some apples are twice as far from the ground as others. For the same mass these twice-as-high apples have
practically the same weight
If your mass, the mass of Earth, and the mass of everything in the solar system were twice as much as it is now, yet everything stayed the same size, your weight on Earth would
quadruple.
Earth is presently accelerating toward the Sun (centripetal acceleration). If the Sun collapsed into a black hole, this acceleration would
remain the same
The force of gravity acting on you will increase if you
stand on a planet with a shrinking radius.
Newton discovered
that gravity is universal
Which of these three produces the greatest tidal effect on you right now?
the Earth
The Earth is closer to the Sun in January than in July, which accounts for the fact that the highest high tides in the Northern Hemisphere occur in
winter