PHYS HW 5

What is the magnitude of Earth's gravitational force on a 1-kg body at Earth's surface? 1 kg 10 N 6.67 × 10^-11 kg 6.67 × 10^-11 N

10 N

What is the magnitude of the gravitational force between two 1-kg bodies that are 1 m apart? 1 kg 10 N 6.67 × 10^-11 N 6.67 × 10^-11 kg

6.67 × 10^-11 N

What is the relationship between the center of gravity and the support base for an object that is in stable equilibrium? The center of gravity must be below the support base. The center of gravity must be in the center of the support base of the object. A vertical line through the center of gravity must pass through the center of the support base. A vertical line through the center of gravity must pass inside the support base of the object.

A vertical line through the center of gravity must pass inside the support base of the object.

Why can't you stand with your heels and back to a wall and then bend over to touch your toes and return to your stand-up position? Your center of gravity does not hang below your support base. Your center of gravity is too high above your support base. A vertical line through the center of gravity of your body is in front of the tips of your toes, which is outside your support base. A vertical line through the center of gravity of your body is behind your heels, which is outside your support base.

A vertical line through the center of gravity of your body is in front of the tips of your toes, which is outside your support base.

Why doesn't the Leaning Tower of Pisa topple over? A vertical line through the center of gravity passes inside its support base. The center of gravity is at the center of the building. The center of gravity is suspended below its support base. A vertical line through the center of gravity passes through the center of its support base.

A vertical line through the center of gravity passes inside its support base.

Why are all tides greatest at the time of a full Moon or new Moon? At full Moon and new Moon, the tides from the Moon and the Sun add because they make a right angle with Earth. At full Moon and new Moon, the tides from the Moon and the Sun partially cancel because they are in line with Earth. At full Moon and new Moon, the tides from the Moon and the Sun add because they are in line with Earth. At full Moon and new Moon, the tides from the Moon and the Sun partially cancel because they make a right angle with Earth.

At full Moon and new Moon, the tides from the Moon and the Sun add because they are in line with Earth.

Find the change in the gravitational force between two planets if the masses of both planets are doubled but the distance between them stays the same.

F = G (m1m2/d^2) before: (2*2)/(2^2) = 1 after: (4*4)/(2^2) = 4 4/1 = 4

Suppose you stood atop a ladder so tall that you were 3 times as far from Earth's center as you presently are. Find the change in your weight.

F = G (m1m2/d^2) distance = 3 3^2 = 9

When is your weight measured as mg? For a mass accelerating upward with an acceleration g near the surface of Earth For a mass near the surface of Earth in free fall For a non-accelerating mass near the surface of Earth For a mass accelerating downward with an acceleration g

For a non-accelerating mass near the surface of Earth

What is a gravitational field, and how can its strength be measured? It is a force field on any body with mass. Its strength is the force per unit mass on a test mass. It is a force field on a body with mass, with direction and magnitude equal to the inverse square of the distance to a test mass. It is a force field in empty space with direction and magnitude equal to the inverse square of the mass of a test mass. It is a force field with direction and magnitude at every point in space. It's strength is the force on a test mass.

It is a force field on any body with mass. Its strength is the force per unit mass on a test mass.

How does the thickness of paint sprayed on a surface change when the sprayer is held twice as far away? It is ¼ as thick. It is ½ as thick. It is twice as thick. It is the same thickness

It is ¼ as thick.

If Earth shrank, but there was no change in its mass, then what would happen to your weight at the surface? It would increase. It would decrease. It would stay the same. It would decrease at first and then increase.

It would increase.

Would the springs inside a bathroom scale be more compressed or less compressed if you weighed yourself in an elevator that was accelerating upward? Downward? Less compressed while accelerating upward, but more compressed while accelerating downward More compressed while accelerating upward and while accelerating downward Less compressed while accelerating upward and while accelerating downward More compressed while accelerating upward, but less compressed while accelerating downward

More compressed while accelerating upward, but less compressed while accelerating downward

Newton viewed the curving of the path of a planet as being caused by a force acting on the planet. How did Einstein view the curved path of a planet? Always at rest In a straight line called a geodesic Moving in curved 4-dimensional spacetime In an ellipse

Moving in curved 4-dimensional spacetime

Would a torque on the Moon occur if the Moon were spherical, with both its center of mass and center of gravity in the same location? Why? Yes. The torque requires a space between the center of mass and the center of gravity. No. The torque requires only a difference in force across the Moon. Yes. The torque occurs even when the center of mass and the center of gravity are at the same location. No. The torque requires a distance between the center of mass and the center of gravity.

No. The torque requires a distance between the center of mass and the center of gravity.

Which has the higher tides: spring tides or neap tides? Why? Neap tides are higher, because the tides from the Moon and Sun add together. Spring tides are higher, because the tides from the Moon and Sun add together. Spring tides are higher, because the tides from the Moon and Sun partially cancel. Neap tides are higher, because the tides from the Moon and Sun partially cancel.

Spring tides are higher, because the tides from the Moon and Sun add together.

Why does the gravity in the Space Shuttle compare with the gravity on Earth the way it does? The Space Shuttle is much closer to the center of the Earth than the surface of the Earth. The Space Shuttle and the surface of the Earth are about the same distance from the center of the Earth. The Space Shuttle is much farther away from the center of the Earth than the surface of the Earth.

The Space Shuttle and the surface of the Earth are about the same distance from the center of the Earth.

Why do the astronauts in the Space Shuttle float around? There is no gravity in the Space Shuttle because it is too far away from the center of the Earth. 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. There is no gravity in the Space Shuttle because it is completely enclosed and shielded from the effects of gravity due to the Earth.

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 is a black hole invisible? A black hole is made of matter that absorbs all wavelengths of light. A black hole is a black dwarf star. The escape velocity of the black hole is greater than the speed of light. A black hole is surrounded by an opaque cloud of dust.

The escape velocity of the black hole is greater than the speed of light.

How does the force of gravity between two bodies change when the distance between them is doubled? The force quadruples. The force is cut in half. The force decreases to ¼ of its initial value. The force doubles.

The force decreases to ¼ of its initial value.

State Newton's law of universal gravitation in words. Then do the same with one equation. The force is proportional to the product of two masses and inversely proportional to the distance between their centers: F ~ m1m2/d. The force is proportional to the product of two masses and to the square of the distance between their centers: F ~ m1m2d2. The force is proportional to the product of two masses and inversely proportional to the square of the distance between their centers: F ~ m1m2/d2. The force is proportional to the product of two masses: F ~ m1m2.

The force is proportional to the product of two masses and inversely proportional to the square of the distance between their centers: F ~ m1m2/d2.

How does the gravity in the Space Shuttle compare with the gravity on Earth's surface? The gravity in the Space Shuttle is much larger than the gravity on Earth's surface. The gravity in the Space Shuttle is much smaller than the gravity on Earth's surface. The gravity in the Space Shuttle is approximately equal to the gravity on the surface of the Earth.

The gravity in the Space Shuttle is approximately equal to the gravity on the surface of the Earth.

Predict how the upward force exerted on the feet by the scale will compare to the man's weight if the elevator is moving downward at a constant speed. The upward force on the feet will exceed the man's weight. The upward force on the feet will be less than the man's weight. The upward force on the feet will be equal to the man's weight.

The upward force on the feet will be equal to the man's weight.

Predict how the upward force exerted on the feet by the scale will compare to the weight of the man if the elevator is moving upward at a constant speed. The upward force on the feet will be equal to the man's weight. The upward force on the feet will be less than the man's weight. The upward force on the feet will exceed the man's weight.

The upward force on the feet will be equal to the man's weight.

Predict how the upward force exerted on the feet by the scale will compare to the man's weight if the elevator is accelerating downward. The upward force on the feet will be equal to the man's weight. The upward force on the feet will exceed the man's weight. The upward force on the feet will be less than the man's weight.

The upward force on the feet will be less than the man's weight.

Predict how the upward force exerted on the feet by the scale will compare to the man's weight if the elevator is accelerating upward. The upward force on the feet will be equal to the man's weight. The upward force on the feet will be less than the man's weight. The upward force on the feet will exceed the man's weight.

The upward force on the feet will exceed the man's weight.

Why are occupants of the International Space Station weightless? They are in free fall. The floor of the space station is made from cavorite, which blocks gravity. Centripetal force cancels gravity in the space station. They are so far from Earth that gravity is essentially zero.

They are in free fall.

Do tides depend more on the strength of gravitational pull or on the difference in strengths? Explain. Tides depend on both the strength and the difference equally. Tides depend weakly on the difference and strongly on the strength. Tides depend only on the difference. Tides depend only on the strength.

Tides depend only on the difference.

Give an example of when your weight is greater than mg. Give an example of when your weight is zero. Your weight is greater than mg when you are on top of a mountain. Your weight is zero when you are in free fall. Your weight is greater than mg when you are accelerating downward. Your weight is zero when you are in free fall. Your weight is greater than mg when you are in free fall. Your weight is zero when you are accelerating upward. Your weight is greater than mg when you are accelerating upward. Your weight is zero when you are in free fall.

Your weight is greater than mg when you are accelerating upward. Your weight is zero when you are in free fall.

What did Newton discover about gravity? The Newtonian synthesis The equation for the force of gravity The law of universal gravitation All of the above

all of the above

According to Newton, the greater the masses of interacting objects, the greater the force between them by the square of the masses. less the gravitational force between them. greater the gravitational force between them.

greater the gravitational force between them.

Where is the center of mass of a hollow soccer ball? At the lowest point of the ball Halfway between the center and the lowest point of the ball In the center of the ball At the top-dead-center of the ball

in the center of the ball

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

no