EXAM 2: ch 4 hw
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°.
What is the force of gravity on a 500-N woman standing on Earth's surface?
500 N
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.
A rock is thrown upward at 50° with respect to the horizontal. As it rises, its vertical component of velocity
decreases
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.
If the radius of the Earth somehow decreased with no change in mass, your weight would
increase
When the distance between two stars decreases by half, the force between them
increases to four times as much
An object is thrown vertically into the air. Because of air resistance, the time for its descent will be
longer than the ascent time
Minimal orbit speed about Earth is about 8 km/s. Minimal orbital speed about Jupiter would be
more than 8 km/s
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 period of a satellite, the time it takes for a complete revolution, depends on the satellite's
radial distance
Newton discovered
that gravity is universal
escape speed for a rocket is less from
the Moon
The fastest moving planet in a solar system is
the planet nearest the sun
A rock is thrown upward at 50° with respect to the horizontal. As it rises, its horizontal component of velocity
remains unchanged.
escape speed for a rocket is greatest from
the sun
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 ball is thrown horizontally from the top of a tall cliff. Three seconds later, the ball has fallen a vertical distance of
45 m
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
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 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°
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.
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.
Earth satellites are typically more than 100-km high so as to mainly be above the Earth's
atmosphere
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
escape speed from Earth is
11.2 km/s
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
According to Newton, the greater the masses of interacting objects, the
greater the gravitational force between them.
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
Minimal orbit speed about Earth is about 8 km/s. Minimal orbital speed about the Moon would be
less than 8 km/s
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 object is placed exactly halfway between the Earth and the Moon. The object will fall toward the
Earth
Dwarf planet Pluto was discovered by perturbations of
Uranus and Neptune.
The planet Neptune was discovered by perturbations of
Uranus.
The Earlybird communication satellite hovers over the same point on Earth's equator indefinitely because
its orbital period is 24 hours
What prevents satellites such as the space shuttle from falling?
nothing, they continually fall around and around Earth
Tangential velocity is velocity
parallel to the surface of 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
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 you would experience no
weight
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
1s
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 projectile is fired horizontally. With no air resistance it maintains its horizontal component of velocity because
no horizontal forces act on it
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