PHY 101 Exam 1 Study Guide

-Explain how Eratosthenes measured the size of the Earth.

Used shadows and geometry.

-Explain how the size of the Moon is measured.

Measured using Earth's shadow during lunar eclipse

-How do we measure the distance to the moon?

Laser ranging (bouncing laser off moon reflectors).

-How do we measure the distance to the Sun?

Parallax from different Earth positions.

-How do we measure the size of the Sun?

Ratio of sun's distance and angular size.

What are the basic steps of the scientific method?

Ask, hypothesize, experiment, analyze, conclude.

-What classifies a scientific hypothesis?

Testable and falsifiable idea.

-Define a fact, a hypothesis, a law, and a theory?

Fact: Agreed-upon observation.

Hypothesis: Educated guess.

Law: Statement of repeated observations.

Theory: Well-tested explanation.

-Explain what a scientific attitude is and why scientists use this as a way of learning.

Open-minded, skeptical, evidence-based.

-Is it possible for science, art, and religion to all be connected?

Can relate; explore different truths.

-Must a person choose between science and religion?

Don't have to choose; different focuses.

-What is pseudoscience?

Claims that seem scientific but aren't tested.

-What is technology?

The application of scientific knowledge for practical purposes

-Tools from science.

-How are science and technology related?

Science builds knowledge; tech applies it.

-How are science and technology different?

Science is everything, tech is man-made

-Science = discovery; Tech = application.

-Why is physics the most basic science?

The concepts of physics are the foundation of other sciences.

-It underlies all other sciences.

-How did Aristotle describe the state of motion of the Earth?

He thought Earth was at rest.

-What did Copernicus believe the relationship between the Sun and Earth?

He believed Earth orbits the Sun.

-What were the findings in Galileo's Lean Tower of Pisa experiment?

Objects fall at same rate regardless of mass.

-What was Galileo's understanding of friction?

Slows motion, not a natural state.

-How did Galileo experiment with inclines to understand motion?

Showed inertia and acceleration.

-Explain the law of inertia.

Objects stay in motion unless acted on.

-How does an object move in the absence of force?

Constant velocity.

-Define force.

A push or pull.

-What is a "net force"?

Total of all forces.

-What does it mean to have zero net force?

No acceleration.

-What is vector quantity vs. scalar quantity?

Vector: Has direction and magnitude.

Scalar: Only magnitude.

-Explain mechanical equilibrium.

No net force; balanced.

-What are the units of force?

Newton (N).

- Explain what a support force is.

Upward force from surface.

-How is weight measured using a scale?

Measures support force.

-When a force acting on an object is net zero does that mean that object is at rest? Why or why not?

Not always; could be constant motion.

-What is the net force acting on an object that is in dynamic equilibrium?

Zero.

-What is the net force acting on an object that is in static equilibrium?

Zero.

-Can you explain why Earth moves at 30km/s but when you jump in the air, you stay with the motion of Earth?

You move with it.

-What does it mean "Motion is relative"?

Motion is always measured relative to something else.

-What is the formula for speed?

Speed = Distance ÷ Time.

-What is instantaneous speed?

Speed = Distance ÷ Time.

-What is Average Speed?

the total distance traveled divided by the total time

-Define velocity.

the speed of something in a given direction.

-Velocity is speed with direction; acceleration is a change in velocity over time.

-What is a quantity that identifies direction and magnitude?

A vector.

-What if it's a quantity that only describes magnitude?

It's a scalar.

-What is the difference between constant velocity and changing velocity?

Constant velocity means same speed and direction; changing velocity means speed or direction (or both) changes.

-What is the formula for Acceleration?

Acceleration = (Final velocity - Initial velocity) ÷ Time → a = Δv / t

-If a runner goes from rest to 10 m/h in 10 s, what is their acceleration?

(10 m/h - 0) ÷ 10 s = 1 m/h per second

Explain how Galileo used slopes to understand acceleration.

He used inclined planes to slow down falling objects, helping him observe how speed changes over time.

When is an object considered in free fall?

When only gravity is acting on it—no air resistance.

Explain why g changes depending on the location of the object:

g is weaker farther from Earth's center or on different planets.

How does friction interfere with the free fall of an object?

Air resistance slows it down, reducing its acceleration.

What are the units for measure of acceleration?

Meters per second squared → m/s²

What is the difference between velocity and speed?

Speed is how fast; velocity is how fast and in what direction.

-What causes an object to accelerate?

A net force

-What must you increase for acceleration to increase?

More net force or less mass

-Is friction a type of force?

Yes

-On object that is moving towards the right has friction from _______?

Opposite to motion

-Is there friction when an object is at rest?

Yes, static friction

-Friction does not depend on speed. Explain this.

Friction doesn't depend on speed because for most surfaces in basic physics (like dry sliding surfaces), the force of friction mainly depends on two things:

The normal force (how hard the surfaces are pressed together), and

The type of surfaces in contact.

-What's the difference between mass and weight?

Mass is amount of matter; weight is force of gravity

-Is weight or mass more fundamental?

Mass

-What is the unit of force?

N (newtons)

-Is acceleration inversely or directly proportional to mass?

Inversely proportional

What is Newton's Second Law?

Force = mass × acceleration (F = ma)

-Acceleration is directly or indirectly proportional to net force?

Directly proportional

-Acceleration is directly or indirectly proportional to mass?

Inversely proportional

-Explain free fall.

Falling with only gravity acting

-What does the letter g mean in terms of acceleration?

Acceleration due to gravity (9.8 m/s²)

-What factors create air resistance when an object is falling?

Speed, shape, surface area

-What is the acceleration of an object that has reached terminal velocity?

0 (no more acceleration)

-Define work. How could we measure work?

Force × distance

-Explain how you would measure power?

Work ÷ time

-Explain what units are used for power.

Watts

-What is energy?

the ability to do work

-What is mechanical energy?

the total energy of motion and position of an object

Kinetic + potential energy

-What is potential energy? Give an example.

Stored energy (ex: rock on a hill)

-What is the equation for potential energy?

PE = mgh

-What is kinetic energy?

energy of motion

-Explain the equation for kinetic energy.

KE = ½mv²

-Compare potential energy and kinetic energy.

potential energy is stored energy and kinetic energy is energy in motion

-What happens to kinetic energy when the speed of something is doubled? How about tripled?

KE with speed doubled? → KE × 4

KE with speed tripled? → KE × 9

-Explain the work-energy theorem.

Work = change in KE

-How does friction relate to kinetic energy?

Friction reduces KE

-In your own words, explain the law of conservation of energy?

Energy can't be created or destroyed

-Can you list a few examples of conservation of energy?

Pendulums, roller coasters

-Explain the conservation of energy in a pendulum swing.

PE turns into KE and back

-What is a lever and how has it helped us conserve energy?

Simple machine to lift things easier

-Explain what a fulcrum is.

Pivot point

-A machine can multiply force at the expense of __________.

Distance

-What is efficiency?

the ratio of output work to input work

Useful work ÷ input work

-How would you calculate the efficiency of a machine?

(Output/Input) × 100

-Why can't a machine be 100% efficient?

Some energy lost as heat

-Where does all energy originate?

The sun

-What is recycled energy?

Reused waste energy

-Explain how Newton described gravity.

Attraction between all masses

-Is the moon falling towards Earth? Explain your answer.

Yes, constantly falling around Earth

-What is the law of universal gravitation?

the force of gravity acts between all objects in the universe

F = G(m₁m₂)/r²

-What is the universal gravitational constant G?

G = 6.67 x 10^-11 N m²/kg².

-Why would you weigh more at sea level vs. on top a mountain?

Stronger gravity at sea level

-If in an elevator with a scale, what happens to the weight measured with the elevator accelerates upward? Why?

Elevator accelerates up? → Scale shows more weight

-What does it mean to be in a state of weightlessness?

Free fall with no support force

-What happens to the ocean tides twice a day?

Rise and fall twice a day