physical science chapter 4
45 m
A ball is thrown horizontally from the top of a tall cliff. Three seconds later, the ball has fallen a vertical distance of
100 m
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?
both hit at the same time
A hunter fires a bullet from a horizontally—held rifle while simultaneously dropping another bullet from the side of the rifle. The bullet to hit the ground first is
50 m/s
A projectile is launched straight upward at 50 m/s. Neglecting air resistance its speed upon returning to its starting point is
remains unchanged
A rock is thrown upward at 50° with respect to the horizontal. As it rises, its horizontal component of velocity
decreases
A rock is thrown upward at 50° with respect to the horizontal. As it rises, its vertical component of velocity
about 28 days
A satellite near Earth makes a full circle in about 90 minutes. Much farther from Earth, say at the distance to the Moon, time for a full circle would be
25 m/s
A softball player determines her pitching speed by throwing a ball horizontally from an elevation of 20 m above the ground. The ball lands 50 m downrange. What is her pitching speed?
both are the same
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?
the same as it was at the top of its path
After a rock that is thrown straight up reaches the top of its path and is starting to fall back down, its acceleration is
Astronaut has four times as much weight as on Earth
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?
its discovery prompted other laws of nature. it provided prediction and discovery of planets. planets aren't cubes with sharp corners.
An outcome of universal gravitation is that
increases
As the gravitational force increases, the relative weight of an object
The elevator moves downward while slowing in speed.
As you found in Part A, your weight will be greater than normal when the elevator is moving upward with increasing speed. For what other motion would your weight also be greater than your normal weight?
greatest, when closest; least, when furthest
At what part of an elliptical orbit does an Earth satellite have the greatest speed? The least speed?
Since the ball leaves the table horizontally, its speed will not affect the time it takes to reach the floor.
Chuck Stone releases a ball near the top of a track and measures the ball's speed as it rolls horizontally off the end of the table. Students make measurements to predict where a can must be placed to catch the ball. How will the ball's speed affect the time it takes to reach the can once the ball leaves the end of the table? (Does a faster ball take a longer time to hit the floor?
weak force
Compared to other fundamental forces, the Universal Gravitational Constant G indicates gravity to be a relatively
four times as much
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
11.2 km/s
Escape speed from Earth is
The gravity in the Space Shuttle is approximately equal to the gravity on the surface of the Earth.
How does the gravity in the Space Shuttle compare with the gravity on Earth's surface?
decrease also
If Earth's mass somehow decreased with no change in its radius, your weight would
1 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
a straight line
If a satellite were beyond Earth's gravity, what path would it follow?
the force you exert on the scale
If you are standing on a scale in an elevator, what exactly does the scale measure?
It falls away from the straight line it would follow if there were no force on it.
In what sense does the Moon "fall"?
gravity is universal
Newton discovered that
Gravitational force is measured with respect to distance from Earth's center; since the workplaces are practically the same distance from Earth's center any difference due to gravity is negligible.
Phil works on the 15th floor of an office building, and his wife Jean works on the 30th floor, which is twice as high as Phil's workplace.Is the force of gravity half as much in Jean's workspace as in Phil's? Explain why or why not.
the gravitational attraction to other planets
Planets wobble in their orbits due to
horizontal
Shruti Kumar projects a ball at an angle of 30∘ above the horizontal. Which component of initial velocity is larger: the vertical or the horizontal?
horizontal
Shruti Kumar projects a ball at an angle of 30∘ above the horizontal. Which of these components undergoes the least change while the ball is airborne?
less than your normal weight at rest
Suppose you are in an elevator that is moving upward. As the elevator nears the floor at which you will get off, its speed slows down. During this time when the elevator is moving upward with decreasing speed, your weight will be __________.
greater than your normal weight at rest
Suppose you are in an elevator. As the elevator starts upward, its speed will increase. During this time when the elevator is moving upward with increasing speed, your weight will be __________.
its tangential velocity causes it to fall around as well as toward Earth
The Moon continually falls toward Earth, but doesn't get closer because
planet nearest the sun
The fastest moving planet in a solar system is the
pluto
The perturbations of Uranus led to what greater discovery?
Jupiter's radius is 10 times the Earth's radius
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
has farther to go. goes slower.
The planet Jupiter takes a longer time to travel around the Sun than Earth because Jupiter
any sustained speed if time isn't a factor.
Traveling from Earth to the Moon requires that a rocket have
Both are the same
Two motorcycle stunt drivers, one light and the other much heavier, ride their motorcycles up and off an inclined ramp at identical speeds. They both rise in the air and land downrange. Neglecting air resistance, the one to attain the greatest height and greatest range is the
increases
Two objects move toward each other due to gravity. As the objects get closer and closer, the force between them
The speed has to be great enough that the distance the projectile falls each second matches the Earth's curvature.
What connection does Earth's curvature have with the speed needed for a projectile to orbit Earth?
It has escape velocity and moves away from the Earth never returning. It then enters an orbit about the Sun.
What happens to an object close to Earth's surface if it is given a speed exceeding 11.2 km/s?
500 N
What is the force of gravity on a 500-newton woman standing on the Earth's surface?
we are able to hear the two balls fall
When Dr. Hewitt releases the two objects, how can we tell whether one of the objects hits the ground first or whether they both hit at the same time?
increases by 4 times as much
When the distance between a pair of stars decreases by half, the force between them
The Space Shuttle is in free fall, so the shuttle and the astronauts inside it are continuously falling toward the Earth. They thus experience apparent weightlessness.
Why do the astronauts in the Space Shuttle float around?
Gravity pulls the same amount on both, and they both drop the same distance.
Why do the two objects hit the table at the relative times that they do?
The Space Shuttle and the surface of the Earth are about the same distance from the center of the Earth.
Why does the gravity in the Space Shuttle compare with the gravity on Earth the way it does?
no horizontal forces act on it.
With no air resistance a projectile fired horizontally maintains its horizontal component of velocity because
trace a curve that matches Earth's curvature .accelerate downward at g as it moves horizontally. return to its starting position and repeat its falling behavior.
Without air resistance, a projectile fired horizontally at 8 km/s from a mountain top will
in the absence of a supporting surface. in a freely falling elevator. momentarily when you step off a chair.
You experience weightlessness
firmly supported on a horizontal surface and in equilibrium
Your weight is equal to mg when you are
nearer the Moon
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?
weight is zero
inside a freely falling elevator your
