PY 131 Chapter 9 Conceptual Academy

A bullet fired from a horizontaly-held rifle hits the ground in 0.6 seconds. It it were fired with twice the velocity, the bullet would have hit the ground in

0.6 s

On Earth's surface Mo who weighs 400 N, measures his weight at the top of a hype-tall tower extending one Earth radius into space, where he measures his weight to be about

100 N

How many tidal bulges would show on the Moon if it had an ocean surface?

2 tidal bulges

A 360-N force acts on an asteroid. When it is three times farther away the force is

40 N

The force due to gravity on a 500-N woman standing on Earth's surface is

500 N

Newton concluded that gravity extends to the

All of these

Earth's gravitational field is strongest at

Earth's surface.

Which model of gravitation is most recent?

Einsteins theory of gravitation

What is a field most related to in this lesson?

Force

If you stood on the surface of Jupiter, your weight would be three times that on Earth, even though Jupiter is 300 times the mass of Earth. How so?

Jupiters radius is 10 times the earth's radius

What happens to the force of attraction between two planets when the distance between them is doubled?

The force decreases to one quarter.

What happens to the force of attraction between two planets when the masses of both are doubled?

The force quadruples.

A black hole is actually

The remains of a giant star that has undergone gravitational collapse.

What effect on your weight occurs if somehow the Sun doubled its mass?

Your weight would not change.

Gravitational force acting on an orbiting spaceship is

\n almost as much as the ship's weight on the Earth's surface.

The direction of Earth's gravitational field is

\n in the same direction as the gravitational attraction.

To be weightless is to be without

a support force.

The gravitational constant is

a very small number

If our Sun were twice as massive, its pull on Earth would double

actually, the suns pull on earth would quadruple

Why are there no tides in an Olympic-sized swimming pool?

all parts of the pool are practically the same distance from the moon

Does Earth gravity act on inhabitants of an orbiting space station?

always

When in an elevator that drops in free fall you'll find that your

apparent weight is zero

Over time, the distribution of dark matter has

become more clumpy.

In this lesson, Earth's gravitational field is represented by

bold-faced g

The gravitational field of the Earth extends

both inside and outside the earth and throughout the entire universe

A clever merchant buys and sells gold by weight at different elevations. Assuming she maintains the same selling price, how would she make a profit?

buy at a high elevation and sell at a low elevation

Suppose you travel down a cave halfway to a planet's center. If the density of the planet is uniform, how has your weight changed compared to its value on the surface?

by one-half

Black holes are essentially

collapsed stars

If the Earth had half its current mass but the same size, your weight would

decrease to one half your original weight

An object located exactly between Earth and the Moon would be more attracted to the

earth

Tiny nano-tidal forces that act on the human body most likely originate from the

earth

Einstein's theory of gravitation, compared with Newton's,

eliminates the role of force.

How far must you travel to remove yourself from Earth's gravity?

forget it; you can't travel far enough

How do tidal forces arise?

from unequal forces acting on different parts of a body

A friction-free immense perfectly flat plane on Earth's curved surface extends thousands of miles from the point of contact. An object set gliding outward from this point of contact eventually slows down because

gravity will pull in a non-perpendicular direction as the block gets farther out on the plane

The chief cause of ocean tides is that the Moon

has a force of gravity that differs on the opposite sides of the planet

If the Moon had twice the diameter but the same mass and same distance from Earth, low tides of Earth's oceans would be

higher?

When Phil Physiker stands on a weighing scale, his support force is

his normal force, N.

Einstein's most famous equations tells us

how matter and energy are related.

If Earth shinks to a smaller diameter while keeping the same mass, your weight would

increase

If Earth's mass increases while its radius remains unchanged, then your weight would

increase also

Two large asteroids in deep space float toward each other due to gravity. As they become closer, their acceleration

increases

When the distance between two planets decreases by half, what happens to the force of gravity between them?

it increases to four times as much

Imagine a tunnel drilled straight down to Earth's other side. With a clear path and no air resistance, what happens to a stone dropped down this tunnel?

it speeds up until it gets to the center of earth

What change in Earth's acceleration around the Sun occurs if the Sun suddenly becomes a black hole?

it would stay the same

If the Moon had twice its mass while remaining in its same orbit ocean tides on Earth would be

larger

If the Moon were twice its distance from Earth, but with the same force of gravity between Earth and the Moon, tidal effects on Earth's oceans would be

less

The constant G in Newton's equation

makes the units of measurement consistent.

At what phase of the Moon are ocean tides lowest?

new or full moon

One's weightless in space has most to do with

no support force.

Consider an alien civilization living in the zero gravity inner space of a perfectly round hollow planet. If a continent-sized hole is cut to allow access to outer space, what happens to their inner space gravitational field?

non-zero, directed away from the hole

A pair of planets attract each other gravitationally. If both their masses double and distance of separation also doubles, the force on them is

none of these

How can there to be only one tide per day on Earth?

none of these

How can all oceans on Earth have high tides simultaneously?

none of these choices are correct

As you double the distance, the gravitational force becomes

one fourth as strong.

What must occur for significant tidal effects from the Moon on a human body?

parts of the body would have to be appreciably closer to the moon than other parts

An apple twice as far from the ground as one on the same tree has a weight of

practically the same weight

If the mass of the Sun and planets were to double, with no changes in size, then your weight on Earth would

quadruple

With increasing distance from the galactic hub, the orbital speeds of stars

remains about the same.

Which of these most increases the force due to gravity on you: Burrow deep inside a planet, or stand on a planet with a shrinking radius?

standing on a planet with a shrinking radius

Tides are the result of Earth being

stretched and elongated by differences in Moon's pulls.

Two large rocks in deep space float toward each other due to gravity. As they get closer, the force gets

stronger

A black hole is invisible due to its

surface escape velocity

Ocean tides on Earth are mainly affected by

the Moon and the Sun.

An immense perfectly flat friction-free bowling alley is centered on Earth's curved surface and extends four kilometers both ways from the point of contact making a total length of 8 kilometers. From one end, a bowling ball is gently released. What happens next?

the ball rolls the full length back and forth indefinitely

Between the Sun and the Earth, which exerts the strongest tidal effect on your body?

the earth

Phil's weight is

the force he exerts on the scale.

How would the force due to gravity change between Earth and the Sun if the Sun suddenly shrunk to a black hole?

the force would be the same

Why do you weigh a little bit less at the bottom of a skyscaper than you do in an open nearby field of the same elevation?

the mass of the building attracts you upward slightly

When a star collapses to become a black hole, what change occurs in its mass?

the mass remains the same

Although both the Moon and the Sun pull on the Earth's oceans, tides are due mostly to the

the moon

In the period of one day, how do ocean tides rise and fall across the planet?

the rise and fall at different times and different heights almost everywhere

Between the Moon and the Sun pulling on the Earth's oceans, which pulls with a greater force?

the sun

What effect does a solar eclipse have on ocean tides?

they are extra high

As the Sun gets closer each January due to Earth's eccentric orbit, what happens to ocean tides?

they get more pronounced

The fact that one side of Moon faces Earth mostly involves

torques

When a force of 450 N acts on an asteroid the direction of that force is

toward the asteroid

What Newton discovered most about gravity is that it is

universal

Between the Moon and an apple held over your head, which exerts a greater tidal effect?

watermelon

The escape velocity is greatest for a star in its

white dwarf stage.

Moon pulls on Earth

with more force on the side nearest Moon.

While flying in a jet plane you feel your normal weight, whereas in an orbiting spaceship you don't, because

you are without support forces

When weighingh yourself at high noon, Earth pulls you downward while the Sun pulls you upward. Why does the Sun NOT affect your weight?

you, the scale, and the earth are in free fall (in orbit) around the sun

An elevator is in free fall. An occupant inside has a weight of

zero

An explorer discover a planet with a thin uniform crust but empty inside. At a point halfway from the surface to the center she finds her weight is

zero

At the Earth's center, its gravitational field is

zero