P199 Homework 4

A gun with a muzzle velocity of 100 m/s is fired horizontally from a tower. Neglecting air resistance, how far downrange will the bullet be 1 s later?

100 m.

Escape speed from Earth is

11.2 km/s.

Two projectiles are fired at equal speeds but different angles. One is fired at an angle of 30° and the other at 60°. With no air resistance, the projectile to hit the ground first will be the one fired at

30°.

A projectile is launched at an angle of 15° above the horizontal and lands downrange. With no air resistance, what other projection angle for the same speed would produce the same downrange distance?

75°.

What is the shape of the orbit when the velocity of the satellite is everywhere perpendicular to the force of gravity?

Circle.

An object is placed exactly halfway between the Earth and the Moon. The object will fall toward the

Earth.

An Earth satellite is in an elliptical orbit. The satellite travels slowest when it is

Farthest from Earth.

Is there change in the force of gravity between two objects when their masses are doubled and the distance between them is also doubled?

There is no change.

The planet Neptune was discovered by perturbations of

Uranus

Dwarf planet Pluto was discovered by perturbations of

Uranus and Neptune.

A rock is thrown upward at 50° with respect to the horizontal. As it rises, its vertical component of velocity

decreases.

The Earlybird communication satellite hovers over the same point on Earth's equator indefinitely because

its orbital period is 24 hours.

A lunar month is about 28 days. If the Moon were closer to Earth than it is now, the lunar month would be

less than 28 days.

Minimal orbit speed about Earth is about 8 km/s. Minimal orbital speed about the Moon would be

less than 8 km/s.

According to Newton, the greater the distance between gravitationally interacting objects, the

less the gravitational force between them.

At some point between Earth and the Moon, the forces due to gravity on a space traveler would be the same. This point is

Nearer the Moon.

An Earth satellite is in an elliptical orbit. The satellite travels fastest when it is

Nearest the Earth.

When the distance between two stars decreases by half, the force between them

increases to four times as much.

Two objects move toward each other due to gravity. As the objects get closer and 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.

Newton discovered

that gravity is universal.

The reason the Moon does not crash into Earth is that

the Moon has a sufficient tangential speed.

Escape speed for a rocket is less from

the Moon.

Escape speed for a rocket is greatest from

the Sun.

The fastest moving planet in a solar system is

the planet nearest the Sun.

After a rock that is thrown straight up reaches the top of its path and is starting to fall back down, its acceleration is

the same as it was at the top of its path.

A ball is thrown upwards and caught when it returns. Neglecting air resistance, the speed with which it is caught is

the same as its initial speed.

Compared to the speed a satellite loses when traveling from nearest to farthest points from Earth, the speed gained when returning from farthest to nearest is

the same.

The speeds of the planets about the Sun depend on

their distances from the Sun.

Planets would crash into the Sun if it weren't for

their tangential velocities.

An Earth satellite is simply a projectile freely falling around the Earth.

true.

Consider two planets in space that gravitationally attract each other. If the mass of one planet is doubled, and the distance between them doesn't change, then the force between them is

twice as much.

Inside a freely falling elevator your

weight is zero.

Inside a freely falling elevator you would experience no

weight.

Strictly speaking, when you step off a curb you are momentarily

weightless.

If the Sun were twice as massive,

-Earth's pull on the Sun would double. -its pull on the Earth would double.

Without air resistance, a projectile fired horizontally at 8 km/s from a mountaintop will

-return to its starting position and repeat its falling behavior. -trace a curve that matches Earth's curvature. -accelerate downward at g (10 m/s) as it moves horizontally.

The circular orbit of a satellite orbiting the Earth is characterized by a constant

-speed. -radial distance. -acceleration.

A bullet fired horizontally hits the ground in 0.5 s. If it had been fired with twice the velocity it would have hit the ground in

0.5 s.

If a projectile is fired straight up at a speed of 10 m/s, neglecting air resistance, the time it takes to reach the top of its path is

1 s.

A woman who normally weighs 400 N stands on top of a very tall ladder so she is one Earth-radius above Earth's surface. What is her weigh there?

100 N.

A ball player wishes to determine pitching speed by throwing a ball horizontally from an elevation of 5 m above the ground. The player sees the ball land 20 m down range. What is the player's pitching speed?

20 m/s.

Ignoring air drag, what is the maximum speed that can be given to a horizontally moving tennis ball as it clears the net 1.25 m high to remain within the edge of the court, which is 12.0 m distant?

24.0 m/s.

A projectile is thrown into the air at an angle of 50° and lands on a target that is at the same level the projectile started. With no air resistance it will also land on the target if it is thrown at an angle of

40°.

A ball is thrown horizontally from the top of a tall cliff. Three seconds later, the ball has fallen a vertical distance of

45 m.

Throw an object at an angle upward. With no gravity it will follow a straight-line path. But because of gravity, at the end of 1 s, it is

5 m below the straight line.

A stone is thrown horizontally from the top of a cliff. One second after leaving your hand it drops a vertical distance of

5 m.

A projectile is launched straight upward at 50 m/s. If air resistance is negligible, its speed upon returning to its starting point is

50 m/s.

What is the force of gravity on a 500-N woman standing on Earth's surface?

500 N.

A- smaller circle around earth B- little bigger circle around earth C- largest circle around earth A. Rank from greatest to least their orbital speeds B. Rank from greatest to least their times to orbit Earth.

A. A is greatest, B, C is least B. C is greatest, B, A is least

Newton's universal law of gravity tells us that F=G(m1m2/d2). Newton's second law tells us that a=Fnet/m. A. With a bit of algebraic reasoning find your gravitational acceleration toward any planet of mass M a distance d from its center. B. Does your gravitational acceleration depend on your mass?

A. a = GM/d^2 B. No

For the astronauts inside an orbiting space vehicle, there is no force of Earth's gravity acting on them. This statement is

Always false.

An astronaut lands on a planet that has the same mass as Earth but half the diameter. How does the astronaut's weight differ from that on Earth?

Astronaut has four times as much weight as on Earth.

An airplane flies at 40 m/s at an altitude of 50 m. The pilot drops a heavy package, which falls and strikes the ground. Neglecting air resistance, where does the package land?

Beneath the plane.

The planet Jupiter is about 300 times as massive as Earth, yet on its surface you would weigh only about 3 times as much. This is because

Jupiter's radius is 10 times Earth's radius.

Earth is farther away from the Sun in June and closest in December. In which of these two months is Earth moving faster around the Sun?

The Earth travels faster about the Sun in December than in June.

An astronaut lands on a planet that has the same mass as Earth but twice the diameter. How does the astronaut's weight differ from that on Earth?

The astronaut weighs one-quarter as much as on Earth.

A hunter aims a rifle at an angle of 10° above the horizontal. The hunter fires a bullet while simultaneously dropping another bullet from the side of the rifle. Which bullet hits the ground first?

The dropped one.

A satellite near Earth makes a full circle in about 90 minutes. How long would a satellite located as far away as the Moon take to orbit Earth?

about 28 days.

A bullet fired from a rifle begins to fall

as soon as it leaves the barrel.

Earth satellites are typically more than 100-km high so as to mainly be above the Earth's

atmosphere.

The International Space Station orbits at an average 360-km altitude so that it is mainly above Earth's

atmosphere.

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 hunter fires a bullet from a horizontally-held rifle while simultaneously dropping another bullet from the side of the rifle. Which bullet hits the ground first?

both hit at the same time.

Two motorcycle stunt drivers, one light and the other much heavier, drive their motorcycles up and off an inclined ramp at identical speeds. They both rise in the air and land downrange. Neglecting air drag, the one to attain the greatest height and greatest range is the

both the same.

A supplier wants to make a profit by buying gold by weight at one altitude and selling it at the same price per kilogram at another altitude. The supplier should

buy at a high altitude and sell at a low altitude.

Acceleration is greatest for a satellite in elliptical orbit when it is

closest to Earth.

If Earth's mass decreased to one-half its original mass with no change in radius, your weight would

decrease to one-half.

If your mass remained the same while the mass of Earth doubled while staying the same size, your weight would

double.

The force of gravity does work on a satellite when it is in

elliptical orbit.

How far must one travel to completely be beyond Earth's gravity?

forget it; you can't travel far enough.

The Sun is spherical due to

gravitation.

According to Newton, the greater the masses of interacting objects, the

greater the gravitational force between them.

If the mass of Earth somehow increased with no change in radius, your weight would

increase also.

If the radius of the Earth somehow decreased with no change in mass, your weight would

increase.

An object is thrown vertically into the air. Because of air resistance, the time for its descent will be

longer than the ascent time.

Compared with the period of satellites in orbit close to Earth, the period of satellites in orbit far from Earth is

longer.

From Earth, one satellite appears to overtake another. The faster satellite is

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 attracts us upward slightly.

A lunar month is about 28 days. If the Moon were farther from Earth than it is now, the lunar month would be

more than 28 days.

Minimal orbit speed about Earth is about 8 km/s. Minimal orbital speed about Jupiter would be

more than 8 km/s.

According to Newton, the closer gravitationally interacting objects are to each other, the

more the gravitational force between them.

Consider a space pod somewhere between Earth and the Moon, at just the right distance so that the gravitational attractions to Earth and the Moon are equal. Is this location nearer Earth or the Moon?

nearer the Moon.

The amount of gravitational force that acts on a space vehicle that orbits Earth is

nearly as much as the vehicle's weight on Earth's surface.

A projectile is fired horizontally. With no air resistance it maintains its horizontal component of velocity because

no horizontal forces act on it.

What prevents satellites such as the space shuttle from falling?

nothing, they continually fall around and around Earth.

Communications and weather satellites always appear at the same place in the sky because these satellites are

orbiting Earth with a 24-hour period.

Tangential velocity is velocity

parallel to the surface of the Earth.

The force of gravity acts on all apples on an apple tree. Some apples are twice as far from the ground. Such twice-as-high apples of the same mass, have

practically the same weight.

The period of a satellite, the time it takes for a complete revolution, depends on the satellite's

radial distance.

Roll a bowling ball off the edge of a table. As it falls, its horizontal component of motion

remains constant.

A rock is thrown upward at 50° with respect to the horizontal. As it rises, its horizontal component of velocity

remains unchanged.

A projectile is fired vertically from the surface of the Earth at 8 km/s and remains in a vertical path. The projectile will

rise and fall back to Earth's surface.