Module 5 Flashcards
What is the interplay between in the history of the universe?
Matter and energy
This interplay began in the Big Bang and continues today.
Who put together the laws describing motion and gravity?
Sir Isaac Newton
He built upon earlier discoveries by Galileo and others.
What are Newton’s three laws of motion?
- An object at rest stays at rest; 2. Force equals mass times acceleration; 3. For every action, there is an equal and opposite reaction.
These laws describe the relationship between forces and motion.
What is the definition of speed?
Distance traveled per unit of time
For example, ‘100 kilometers per hour’ indicates speed.
What is the difference between speed and velocity?
Velocity includes both speed and direction
For example, ‘100 kilometers per hour going due north’ describes velocity.
What is acceleration?
Change in velocity over time
Acceleration can occur due to changes in speed or direction.
What is the acceleration of gravity on Earth?
Approximately 9.8 m/s²
This value means objects fall faster by this amount each second.
What is momentum?
The product of mass and velocity
Momentum is a key concept in understanding collisions.
What is a net force?
The overall force acting on an object
A net force that is not zero causes acceleration.
What is angular momentum?
Momentum of an object in circular motion
It can change only when a torque is applied.
What is torque?
A twisting force that can change angular momentum
The effectiveness of torque depends on the point of application.
How is mass different from weight?
Mass is the amount of matter; weight is the force due to gravity acting on that mass
Weight can vary based on the gravitational force acting on the mass.
What happens to weight in an accelerating elevator?
Weight increases when accelerating upward and decreases when accelerating downward
Mass remains constant, but weight changes due to forces.
What is weightlessness?
The condition of free-fall where no support force acts on the body
You experience weightlessness when falling freely.
Fill in the blank: The acceleration due to gravity on Earth is _______.
9.8 m/s²
True or False: A feather and a rock fall at different rates due to gravity.
False
Both fall at the same rate in a vacuum without air resistance.
What is the relationship between force and momentum?
A force is required to change an object’s momentum
This principle is critical in understanding collisions.
What principle did Galileo demonstrate regarding gravity?
Gravity accelerates all objects equally regardless of mass
This was shown through his experiments with falling objects.
What does it mean to be in free-fall?
You are in free-fall whenever there’s nothing to prevent you from falling.
What is the sensation experienced during free-fall?
The sensation of weightlessness.
Why are astronauts weightless in the International Space Station?
They are in a constant state of free-fall.
What common misconception do people have about gravity in space?
Many believe there is no gravity in space.
What is the acceleration of gravity at the altitude of the Space Station’s orbit?
About 10% less than on Earth’s surface.
What happens when an object travels at a constant velocity in space?
No net force is acting upon it.
What are Newton’s three laws of motion?
- An object moves at constant velocity if no net force acts on it.
- F = ma (force equals mass times acceleration).
- For every action, there is an equal and opposite reaction.
What does Newton’s First Law state?
An object moves at constant velocity if there is no net force acting upon it.
What does Newton’s Second Law quantify?
The relationship between force, mass, and acceleration.
What is the standard unit of force?
Newton.
True or False: Weight is a unit of mass.
False.
What does Newton’s Third Law state?
For any force, there is always an equal and opposite reaction force.
What is the law of conservation of momentum?
The total momentum of interacting objects cannot change without external forces.
What happens to an object when a net force is applied?
It accelerates in the direction of the force.
Fill in the blank: The faster you run out of the tower, the farther you’d go before landing. If you could run fast enough, you would be _______.
orbiting Earth.
How did Newton’s insight about gravity change our understanding of the universe?
It eliminated the distinction between earthly and heavenly motion.
What is the relationship between mass and weight in a gravitational field?
Weight is the force of gravity acting on mass.
What is the effect of air resistance on falling objects?
It can alter their motion, causing them to fall slower.
What did Newton discover about motion and gravity?
Gravity operates in both the heavens and on Earth.
What is the significance of Newton’s work published in 1687?
It revolutionized mathematics and science, detailing the laws of motion and gravity.
True or False: Astronauts feel the sensation of free-fall the entire time they are in orbit.
True.
What is the primary reason a car comes to a stop on Earth?
Forces arising from friction and air resistance.
What happens to the ball when the string breaks while swinging it around your head?
The ball flies off in a straight line.
What is the effect of gravity on a planet in orbit around the Sun?
It creates an inward acceleration.
Fill in the blank: The laws of motion govern everything from daily movements on Earth to the movements of _______.
planets, stars, and galaxies.
What is the relationship between force and acceleration as per Newton’s Second Law?
Force equals mass times acceleration (F = ma).
What are the implications of Newton’s Third Law in terms of gravitational attraction?
Objects always attract each other through gravity.
What does the law of conservation of momentum state?
The total momentum of interacting objects is conserved as long as there are no external forces acting on them.
An individual object’s momentum can change only if another object’s momentum changes by an equal and opposite amount.
How does Newton’s second law relate to conservation of momentum?
It explains how one object exerts a force on another, changing the second object’s momentum, while the first object’s momentum changes by the same amount in the opposite direction.
This interaction illustrates how momentum is transferred between objects.
What is an example of conservation of momentum in action?
A rocket engine firing, where the momentum gained by the rocket is equal to the momentum lost by the gases ejected backward.
This demonstrates that forces between the rocket and gases are equal and opposite.
What keeps a planet rotating and orbiting the Sun?
The law of conservation of angular momentum states that total angular momentum cannot change without external torque.
An individual object can change its angular momentum only by interacting with another object.
What is the formula for calculating Earth’s angular momentum in orbit?
Angular momentum = m * v * r, where m is mass, v is orbital velocity, and r is the distance from the Sun.
This formula shows how angular momentum is dependent on both speed and distance from the Sun.
According to Kepler’s second law, what happens to Earth’s orbital speed as it approaches the Sun?
Earth moves faster when it is nearer to the Sun and slower when it is farther away.
This is due to the conservation of angular momentum.
What is the law of conservation of energy?
Energy cannot be created or destroyed, only transformed or exchanged between objects.
This principle governs all interactions involving energy in the universe.
What are the three major categories of energy?
- Kinetic energy
- Radiative energy
- Potential energy
These categories encompass most forms of energy encountered in various contexts.
What is kinetic energy?
The energy of motion, calculated as KE = 1/2 mv^2, where m is mass and v is speed.
Examples include falling rocks and orbiting planets.
What is potential energy?
Stored energy that can be converted into kinetic or radiative energy, such as gravitational potential energy.
An example is a rock perched on a ledge.
What is thermal energy?
The collective kinetic energy of many particles moving randomly within a substance.
It is related to temperature but is distinct from it.
How does temperature relate to thermal energy?
Temperature measures the average kinetic energy of particles, while thermal energy measures total kinetic energy.
Higher temperature indicates faster-moving particles.
What is gravitational potential energy?
The potential energy of an object depending on its mass and height above the ground, calculated as PE = mgh.
It decreases as the object falls, converting into kinetic energy.
What does Einstein’s equation E=mc^2 represent?
It describes the equivalence of mass and energy, stating that a small amount of mass can be converted into a large amount of energy.
This principle is fundamental in nuclear reactions.
Fill in the blank: Energy can be converted from one form to another, but it can never be ______.
created or destroyed.
True or False: The total momentum of a system can change if external forces are applied.
True.
What is the relationship between angular momentum and rotational speed in a contracting object?
As an object contracts, its rotational speed increases to conserve angular momentum.
This principle is observable in ice skaters pulling in their arms.
How does thermal energy transfer differ between air and water at the same temperature?
Water, being denser, transfers thermal energy more effectively than air at the same temperature.
This is why boiling water burns faster than hot air.
What is the energy release from a 1-megaton H-bomb due to mass conversion?
Approximately 0.1 kilogram of mass is converted into energy.
How does the Sun generate energy?
By converting a tiny fraction of its mass into energy through nuclear fusion.
What does Einstein’s formula indicate about mass and energy?
Mass can be converted into energy and energy can be transformed into mass.
From where does an object’s energy ultimately originate?
All energy can be traced back to the Big Bang.
What are the three basic categories of energy?
Kinetic, radiative, and potential energy.
What does the law of conservation of energy state?
Energy cannot be created or destroyed.
What is Newton’s universal law of gravitation?
Every mass attracts every other mass through gravity, with force proportional to the product of their masses and inversely proportional to the square of the distance between them.
What happens to the gravitational force if the distance between two objects is doubled?
The gravitational force decreases by a factor of 4.
How did Newton’s laws extend Kepler’s laws?
Newton showed that Kepler’s laws are consequences of the laws of motion and the universal law of gravitation.
What shapes can bound orbits take?
Ellipses (including circles).
What are unbound orbits?
Paths that bring an object close to another object just once, which can be parabolas or hyperbolas.
What is the common center of mass in a gravitational system?
The point at which two objects would balance if connected.
How can we determine the mass of a distant object using Kepler’s third law?
By measuring the orbital period and distance of another object orbiting around it.
What is the primary means of determining masses throughout the universe?
Newton’s version of Kepler’s third law.
What is orbital energy composed of?
The sum of kinetic energy and gravitational potential energy.
What is a gravitational encounter?
An interaction where two objects pass near enough to exchange energy.
What effect does atmospheric drag have on satellites?
It causes satellites to lose orbital energy until they re-enter the atmosphere.
Fill in the blank: The gravitational force follows an _______.
inverse square law.
True or False: Orbits can change spontaneously without external influence.
False.
What effect does friction have on a satellite in low-Earth orbit?
Friction causes the satellite to lose orbital energy, leading it to eventually plummet to Earth.
The satellite’s lost orbital energy is converted to thermal energy in the atmosphere, causing it to burn up during re-entry.
How might friction explain the presence of small moons around outer planets?
Friction may have slowed objects passing through gas clouds surrounding outer planets, allowing some to be captured as moons.
Mars may have captured its two small moons in a similar manner.
What is escape velocity?
The minimum velocity required for an object to escape Earth’s gravity from the surface, approximately 11 km/s.
Escape velocity does not depend on the mass of the escaping object.
True or False: Escape velocity is the same regardless of the object’s starting altitude.
False.
Escape velocity depends on whether you start from the surface or a higher altitude.
What causes tides on Earth?
The gravitational attraction between Earth and the Moon creates tidal forces that result in two tidal bulges on Earth.
This is due to the difference in gravitational pull on different parts of Earth.
What are the two daily high tides a result of?
The rotation of Earth through the two tidal bulges created by the Moon’s gravitational pull.
Fill in the blank: The Sun’s tidal force on Earth is _______ than that of the Moon.
less
The Sun’s tidal force is less than half as strong as that from the Moon due to the greater distance.
What do spring tides occur?
When the tidal forces of the Sun and Moon work together at new moon and full moon.
What are neap tides?
Relatively small tides that occur when the tidal forces of the Sun and Moon counteract each other at first- and third-quarter moons.
What is tidal friction?
Friction caused by the stretching of Earth due to tidal forces, which affects Earth’s rotation and the Moon’s orbit.
How does tidal friction affect Earth’s rotation?
It gradually slows Earth’s rotation and increases the Moon’s orbital energy and distance.
What is synchronous rotation?
A phenomenon where the same face of an object, like the Moon, always points toward the body it orbits.
How does tidal friction lead to synchronous rotation of the Moon?
The tidal forces from Earth slowed the Moon’s rotation until it matched its orbital period.
What is the result of tidal forces on other celestial bodies?
Synchronous rotation is common, affecting moons and binary star systems.
What is the relationship between mass and the acceleration of falling objects?
The acceleration of a falling object is independent of its mass.
Who first discovered that the acceleration of falling objects does not depend on mass?
Galileo.
What did Einstein’s general theory of relativity explain about falling objects?
It revealed that the independence of falling object acceleration from mass is not a coincidence, but a deeper truth about gravity.
How does the gravitational acceleration in low Earth orbit compare to that at Earth’s surface?
It is only about 10% less than the acceleration of gravity at Earth’s surface.
What causes astronauts to be weightless in orbit?
They are in free-fall, not due to a lack of gravity.
