Homework 5

The fastest moving planet in a solar system is

the planet nearest the Sun.

The Sun is spherical due to

gravitation

Two objects move toward each other due to gravity. As the objects get closer and closer, the force between them

increases.

If the Sun were twice as massive,

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

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.

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

less the gravitational force between them.

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

What prevents satellites such as the space shuttle from falling?

nothing, they continually fall around and around 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.

If your mass and the mass of Earth remained the same while the Earth's radius was halved, your weight would

quadruple

If your mass remains unchanged while both the mass of Earth and its radius doubles, your weight

reduces by half.

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.

Weight can be simulated in a space vehicle if the vehicle is

rotating.

Newton discovered

that gravity is universal.

Escape speed for a rocket is less from

the Moon.

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

Inside a freely falling elevator you would experience no

weight.

Passengers in a high-flying jumbo jet feel their normal weight in flight. Passengers in an orbiting space vehicle do not because passengers are

without support forces.

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°

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

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

1 s

Escape speed from Earth is

11.2 km/s.

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

Earth.

The planet Neptune was discovered by perturbations of

Uranus.

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

always false.

In the vacuum of outer space, there is no

atmospheric pressure.

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

decrease.

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

decreases.

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

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

500 N

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

atmosphere

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

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

forget it; you can't travel far enough

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

four times as much.

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

less than 8 km/s

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