Exam 3 Ch 5
A gun with a muzzle velocity of 100 m/s is fired horizontally from a tower. Neglecting air resistance, where will the bullet be 1 s later?
100 m downrange
The ground speed of an airplane that has an airspeed of 100 km/h when it is in a 100-km/h crosswind is
141 km/h.
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
A projectile is launched at 60° above ground level. What other angle at the same speed will result in the same range?
30°.
If you drop a ball from rest it will fall 5 meters in one second. If you toss the ball horizontally it will fall in one second a vertical distance of
5 m
What is the force of gravity on a 500-N woman standing on Earth's surface?
500 N
Which depends on gravity - weight or mass?
Weight depends on gravity
When is your weight equal to mg?
When you are in a state of zero acceleration on the Earth's surface.
When is your weight greater than mg?
When you are in an elevator that accelerates upward near the Earth's surface.
When is your weight zero?
When you are in free fall.
Occupants in a rotating donut-like space habitat experience weight due to
a support force.
Two objects move toward each other because of gravity. As the objects get closer and closer, the force between them
increases.
An Earth satellite is in an elliptical orbit. The satellite travels fastest when it is
nearest Earth.
Is it correct to say that the planets of the solar system are simply projectiles falling around the Sun?
yes
A very massive object A and a less massive object B move toward each other under the influence of gravitation. Which force, if either, is greater?
both forces are the same.
Earth's gravitational field extends
both inside and outside the Earth and throughout the entire universe
What does "centripetal" mean?
Center-seeking.
An object is placed exactly halfway between Earth and the Moon. The object will fall toward the
Earth.
Inside a freely falling elevator, there would be no
apparent weight for you.
earth satellites are typically more than 100 km high so as to be above Earth's
atmosphere.
When the distance between two planets is doubled, the force of attraction between them
decreases to one quarter.
According to Newton, the greater the masses of interacting objects, the
greater the gravitational force between them.
Minimal orbit speed about Earth is about 8 km/s. Minimal orbital speed about the Moon would be
less than 8 km/s.
A "weightless" astronaut in an orbiting shuttle is
like the shuttle, pulled by Earth's gravitation.
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.
The constant G in Newton's equation for universal gravitation
makes the units of measurement consistent.
The ______ of an object is a measure of the amount of matter it contains. On the other hand______is a measure of gravitational force on an object.
mass, weight
Communications and weather satellites always appear at the same place in the sky. This is because these satellites are
orbiting Earth with a 24-hour period.
The force of gravity acts on all apples on an apple tree. Some apples are twice as far from the ground as others. These twice-as-high apples, for the same mass, have
practically the same weight.
A projectile is launched vertically at 50 m/s. If air resistance is negligible, its speed upon returning to its starting point is
50 m/s.
A bullet is fired horizontally with an initial velocity of 300 m/s from a tower that is 20 m high. If air resistance is negligible, the horizontal distance the bullet travels before hitting the ground is
600 m.
If Earth's mass decreased to one-half its original mass with no change in radius, then your weight would
If Earth's mass decreased to one-half its original mass with no change in radius, then your weight would
A ball is thrown upward and caught when it comes back down. Neglecting air resistance, the speed with which it is caught is
the same as the speed it had when thrown upward.
Where is your gravity detector?
Inside your ear.
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
What is the effect of air drag on the height and range of batted baseballs?
The effect of air drag is that both range and height are decreased.
When you whirl a can at the end of a string in a circular path, what is the direction of the force that acts on the can? Neglect the downward pull of gravity.
The force is directed toward the center of the circle.
An Earth satellite is simply a projectile freely falling around the Earth.
True
Is it possible to simulate weight in a space habitat?
Yes, weight can be simulated with the centripetal force acting on a person moving in a circular path.
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.
When the masses of two planets are doubled, the force of attraction between them
quadruples.
A projectile is fired vertically from the surface of Earth at 10 km/s. The projectile will
rise and fall back to Earth's surface.
A projectile is fired vertically from the surface of Earth at 8 km/s. The projectile will
rise and fall back to Earth's surface.
One's weightlessness in space involves no
support force.
A hunter aims a rifle at an angle of 10° below the horizontal. The hunter fires a bullet while simultaneously dropping another bullet from the level of the rifle. Which bullet will hit the ground first?
the fired one
Planets would crash into the Sun if it weren't for
their tangential velocities