Apologia Physical Science Module 11 Study Guide

Name the four fundamental forces in creation. Which two forces are really different aspects of the same force?

Gravitational force, the weak force, the strong force, and the electromagnetic force. The electromagnetic force and the weak force are really different facets of the same force.

Which is the weakest of the fundamental forces? Which is the strongest?

Gravitational force is the weakest, the strongest is the strong force

Name the three principles of Newton's Universal Law of Gravitation.

1. All object with mass are attracted to one another by gravitational force.

2. The gravitational force between two masses is directly proportional to the mass of each object.

3. The gravitaional force between two masses is inversely proportional to the square of the distance between those two objects.

The gravitational force between two objects (mass = 10 kg, mass = 6 kg) is measured when the objects are 10 centimeters apart. If the 10 kg mass is replaced with a 20 kg mass and the 6 kg mass is replaced with a 12 kg mass, how does the new gravitational force compare to the first one that was measured?

When the 10 kg mass is replaced by a 20 kg mass, the mass doubled. This doubles the gravitational force. The 6 kg mass is also doubled to 12 kg. This once again doubles the gravitational force. Thus, the total change is 2x2 = 4. The new gravitational force, then, is 4 times larger than the old one.

The gravitational force between two objects (mass = 10 kg, mass = 6 kg) is measured when the objects are 10 centimeters apart. If the distance between them is increased to 40 centimeters, how does the new gravitational attraction compare to the first one that was measured?

The only difference between the first and second situation is the distance between the objects was multiplied by 4. The gravitational force decreases when the distance between the objects increases, and it decreases according to the square of that increase. Thus, the force is divided by 4 squared, which is 16. The new gravitational force, then, is 16 times smaller than the old one.

The gravitational force between two objects (mass = 1 kg, mass = 2 kg) is measured when the objects are 12 cm apart. If the 1 kg mass is replaced with a 5 kg mass, the 2 kg mass is replaced with a 4 kg mass, and the distance between the objects is reduced to 4 cm, how does the new gravitational force compare to the first one that was measured?

When the 1 kg mass is replaced by a 5 kg mass, the mass was multiplied by 5. This multiplies the gravitational force by 5. The 2 kg mass is doubled to 4 kg. This doubles the gravitational force. The distance betweent eh objects was divided by 3. The gravitational force increases with decreasing distance between the objects. The increase goes as the square of the change in the distance. Thus, the force is multiplied by 3 squared, which is 9. Therefore, the total change is 5x2x9 = 90. The new gravitational force, then, is 90 times larger than the old one.

If Venus orbits the sun because the sun exerts a gravitational force on it, what is the equal and opposite force required by Newton's Third Law of Motion?

The equal and opposite force is the gravitational force that Venus exerts on the sun.

What kind of force is necessary for circular motion? Give the definition of that force.

Centripetal force is required for circular motion.

Centripetal force - The force necessary to make an object move in a circle. It is perpendicular to the velocity of the object, which means it points toward the center of the circle.

What are the three principles of circular motion?

1. Circluar motion requires centripetal force.

2. The larger the centripetal force, the faster an object travels in a circle of a given size.

3. At a given speed, the larger the centripetal force, the smaller the circle.

In an Olympic event called the "hammer throw," an athlete twirls a massive ball on the ends of a wire. Once he gets the ball twirling very quickly, the athlete releases the wire, allowing the ball to fly straight out into the field. The person who throws the ball the farthest this way is the winner.

A. As the athlete twirls the ball faster and faster, will the wire have to apply more, less, or the same amount of centripetal force?

B. Suppose the athlete starts by gripping the wire close to the ball so tte ball sweeps out a small circle. Then, keeping the spped of the ball constant, he allows some of the wire to slip through his hands so the ball sweeps out a larger and larger circle. Will the wire exert more, less, or the same amount of force as the athlete makes his adjustment?

The wire is exerting the centripetal force. Thus, the force it exerts will change as needed by the principles of circular motion.

A. The wire will need to exert more force because objects that travel fast need large centripetal force.

B. The wire will exert less force, because the larger the centripetal force, the smaller the circle. Thus, the larger circle needs less centripetal force (for the same speed).

What is "centrifugal force?"

It is a myth. There is no such force. The supposed effect of centrifugal force is just Newton's First Law.

List the inner planets and the outer planets.

Inner planets - Mercury, Venus, Earth, Mars

Outer planets - Jupiter, Saturn, Uranus, Neptune

List the planets of the solar system from the closest to the sun to the farthest from the sun.

Mercury, Venus, earth, Mars, Jupiter, Saturn, Uranus, Neptune

List the planets that have rings.

Saturn, Uranus, Jupiter, and Neptune

Where are most of the asteroids in the solar system?

Most of the asteroids are between the orbits of Mars and Jupiter. (Asteroid belt)

What causes an asteroid to become a meteor?

Perturbations in its orbit cause an asteroid to become a meteor.

What are the three parts of a comet? Which of those parts is always present in a comet?

A nucleus, a coma, and a tail. The nucleus is always present.

During what part of a comet's orbit are all three parts present?

All three parts of a comet are present when the comet is close to the sun.

Are comet's orbits circular or elliptical?

Elliptical

Where do most physicists think short-period comets come from?

A mass of objects called the Kuiper belt

What casues gravity, according to Einstein's Theory of General Relativity?

According to General Relativity, gravity is caused by the fact that objects with mass bend space and time.

What causes gravity, according to the gravitation theory?

According to the gravitation theory, gravity is caused by the exchange of particles called "gravitons."