1. Feather
   Bowling ball
2. Baseball
   They would all fall at the same rate.

If it weren't for air resistance, all objects would fall to earth at the same exact rate. The force of gravity acting on an object increases with that object's mass. That ensures that all objects maintain an acceleration of 9.81 m/s/s. Astronaut David Scott conducted an experiment on the moon, where he dropped a hammer and a feather. Both landed at the exact same time.

1. A cyclist moving at a constant speed
   The ISS orbiting the Earth
2. A dog running across a field
   A broken down car sitting in the driveway

Momentum can be thought of as mass in motion. Therefore, if an object doesn't have both mass and velocity, then it does not have momentum. Since a broken-down car has a velocity of zero, it also has a momentum of zero.

1. Float
   Sink
2. Dissolve
   Suspend

The object (or fluid) with the greatest density will always sink to the bottom. This is why your salad dressing always separates. Oil is less dense than vinegar and sinks to the bottom of the container.

1. Gravitational
   Tension
2. Applied
   Spring

In the absence of air resistance, the only force acting upon the ball is gravity. Of course, if you do this on the moon, there will be less gravitational energy!

1. Absolute Zero
   -5,000 degrees Celsius
2. -5,0000 degrees Kelvin
   0 degrees Celsius

At the theoretical temperature of absolute zero, atoms would stop moving. At this point, there is no kinetic energy, which is what creates heat in a substance. If there is nothing moving, then there is no heat. Absolute zero is equivalent to minus 273.15 degrees on the Celsius scale, minus 459.67 degrees on the Fahrenheit scale, and 0 degrees on the Kelvin scale.

1. There'll be one North magnet and one South magnet.
   There'll be two identical magnets - just smaller than the original.
2. It will no longer be a magnet.
   The North and South ends will switch.

If you break a bar magnet in half, you'll get two smaller bar magnets. The North and South ends will arrange themselves in the following way: %0DBefore: N======S %0DAfter: N===S N===S

1. Loudness of the sound
   Pitch of the sound
2. Properties of the medium through which the sound is traveling
   Amplitude of the sound wave

The speed of a wave is most dependent upon the properties of the medium a sound is traveling through, not the properties of the wave itself. Sound travels much faster through water than it does through air.

1. Neutron
   Proton
2. Electron
   Photon

Protons are positively charged particles, located in the neutron of an atom. The number of protons in the nucleus determines the type of element an atom is, regardless of how many neutrons or electrons there are.

1. Frequency
   Wavelength
2. Amplitude
   Trough

The number of waves produced each second is the frequency of the wave, measured in hertz. The frequency of a sound wave affects the pitch of the sound: the higher the frequency, the higher the pitch.

1. Ohm
   Ampere
2. Lumen
   Joule

Some materials allow current to flow through better than others. A material's tendency to resist the flow of charge is called its resistance, and it's measured in ohms. 1 Ohm is the resistance between two points in a conductor where the application of 1 volt will push 1 ampere, or 6.241×1018 electrons.

1. 1
   2
2. 3
   4

A neutral hydrogen atom contains exactly one proton and one electron. It is the simplest element in the universe and makes up about 75% of the baryonic mass of the universe.

1. Mass to Weight
   Mass to Volume
2. Inertia to Mass
   Volume to Weight

Density is a measure of how tightly packed matter is. Density can be found by finding the mass of an object and dividing that by its volume.

1. Lifting the 20 kg crate
   Lifting the 30 kg crate
2. Neither require work.
   Both require the same amount of work.

The force of gravity acting on the 20 kg crate is about 200 N. The force of gravity acting on the 30 kg crate is about 300 N. %0DW = F x d%0DWork done on 20 kg crate = 200 x 3, which is about 600 Joules of work.%0DWork done on 30 kg crate = 300 x 2, which is also about 600 Joules of work.

1. Pascal
   Watt
2. Newton
   Meter

Pressure is defined as the amount of force exerted over a given area. You can create a lot of pressure by exerting a lot of force, or exerting a smaller force over a small area. This idea is why a magician can lie on a bed of nails: he total surface area of all the nail tips together is large enough.

1. 0 m/s/s
   60 m/s/s
2. 600 m/s/s
   6 m/s/s

An acceleration is a change in velocity. If the velocity doesn't change, then there is no acceleration. Because of this, the acceleration of the car going 60 mph has an acceleration of zero.

1. 22 Joules
   11 Joules
2. 0 Joules
   44 Joules

The total energy must remain the same. Since the ball begins with a potential energy of 22 Joules and a kinetic energy of 0 Joules (if there is no movement, then there is no kinetic energy), the total energy of the baseball is 22 Joules. As the ball falls, some of its potential energy is converted to kinetic energy. When it finally reaches the ground, all of its potential energy is converted to kinetic energy, making its kinetic energy 22 Joules.

1. A 30 kg object at a height of 5 meters
   A 10 kg object at a height of 10 meters
2. A 10 kg object at a height of 20 meters
   A 100 kg object at a height of 1 meter

Gravitational potential energy is a product of mass, gravity, and height above the earth. Gravitational PE for a 10 kg object at a height of 20 meters is 2,000 Joules.

1. Gravitational
   Air resistance
2. Both are equal.
   Some other force acts during terminal velocity.

Terminal velocity is reached when the force of air resistance reaches the same magnitude as the force of gravity. Once these forces are balanced, the skydiver no longer accelerates and will continue to fall at constant velocity.

1. More than the neutral atom
   Fewer than the neutral atom
2. The same number as the neutral atom
   Exactly zero, no matter the ion

Because electrons are negatively charged, if an atom loses one (or more), it will become positively charged. On the flip side, if an atom gains electrons, it will become more negative.

1. Proton
   Neutron
2. Electron
   Quark

The nucleus of an atom is made of protons and neutrons. Protons and neutrons are made up of quarks. Electrons orbit the outer edge of an atom and are not found in the nucleus.

1. Voltage
   Current
2. Resistence
   Joule

Voltage is the difference in potential energy between two points in a circuit. This difference in energy creates pressure that forces charged electrons to flow in an electrical circuit.

1. Its momentum doubles.
   Its momentum quadruples.
2. Its momentum remains unchanged.
   Its momentum is zero.

Momentum is directly related to the velocity of an object. So for the same mass, a doubling of the velocity will lead to doubling the momentum.

1. 13 kg
   80 kg
2. 40 kg
   30 kg

Mass represents the amount of matter in an object. The amount of matter, and therefore the mass, does not change as it moves from location to another. So if you have a mass of 80 kg on Earth, you'll also have a mass of 80 kg on the moon.

1. A satellite circling earth at a constant speed
   A ball speeding up as it is thrown
2. A ball slowing down as it is caught
   A hockey puck sliding across ice in a straight line at a constant speed

Velocity is a vector quantity. This means that the direction is just as important as the magnitude when describing velocity. Therefore, any change in speed or direction is a change in velocity (and an acceleration). Since the hockey puck is maintaining constant speed and constant direction, it is NOT accelerating.

1. 9.8 m/s/s
   More than 9.8 m/s/s
2. Less than 9.8 m/s/s
   It depends on the direction of the throw.

The acceleration will still be 9.8 m/s/s. After the rock is thrown, the only force acting on it is gravitational force. This force creates an acceleration of 9.8 m/s/s.

1. The more massive player
   The less massive player
2. They experience the same change in momentum.
   There is no change in momentum for either player.

Each player experiences the same force, thanks to Newton's 3rd law of motion. They also experience this force for the same amount of time. This means that they experience the same impulse and the same change in momentum.

1. Polarization
   Diffraction
2. Dispersion
   Refraction

When a beam of light strikes molecules in the atmosphere, it bounces off in different directions. This happens millions of times before the beam gets to your eyeballs. At sunset, the light takes a much longer path through the atmosphere to your eye than it does at noon. This creates that reddish-orange hue that we all see.

1. Cyan, magenta and green
   Orange, yellow and violet
2. Red, green and blue
   Red, blue and yellow

The primary colors of light are red, green and blue. When red and blue light are combined, you will see magenta. When green and blue light are combined, you will see cyan. Red and green light combine to make yellow. And when all three primary colors of light are combined, you will see white light.

1. Polonium
   Radium
2. Uranium
   Hydrogen

Radioactivity is a measure of how unstable an atom's nucleus is. An unstable nucleus sheds energy so that it can shift to a more stable configuration. Every element from 84 and up is radioactive, with no stable isotope. Polonium is so radioactive that it glows blue.

1. Normal
   Tension
2. Applied
   Friction

The normal force will be as large as necessary to prevent the book from penetrating the table. Normal force gets its name because it refers to a perpendicular arrangement.

1. A 50 kg object with a velocity of 4 m/s
   A 10 kg object with a velocity of 10 m/s
2. A 20 kg object with a velocity of 5 m/s
   A 100 kg object with a velocity of 1 m/s

The formula for kinetic energy is 1/2 times mass time velocity squared. Performing the calculations gives a kinetic energy of 500 joules for the 10 kg object moving at velocity of 10 m/s.

1. 1st
   2nd
2. 3rd
   Law of Gravitation

Newton's 3rd law (For every action, there is an opposite and equal reaction) explains why a rearward force also results in a forward-facing force. The propeller pushes on the air, but the air pushes back on the plane, moving it forward.

1. Displacement
   Velocity
2. Acceleration
   Speed

Vectors require both magnitude and direction. Displacement, velocity and acceleration all express both magnitude (meters, m/s, and m/s/s) and direction, sometimes represented using negative or positive symbols. Speed describes a magnitude (m/s), but does not indicate a direction.

1. 400 km/h
   300 km/h
2. 500 km/h
   700 km/h

When an airplane moves within a medium which is moving relative to the ground, the speed of the airplane(as measured by its speedometer) will not be the same as the speed as measured by a person on the ground (groundspeed). The groundspeed can be determined by adding the airplane's speed and wind speed as vectors.

1. Deuterium
   Tritium
2. Protium
   Bietium

The nucleus of every hydrogen atom contains exactly one proton. However, the nucleus can also contain a varying number of neutrons. Protium is a hydrogen atom without any neutrons. Deuterium contains one neutron, and tritium contains two neutrons. Tritium is the most rare of the three isotopes, and also radioactive.