Physics Test #2 (Chapter 4-7)

Centripetal force (circular)

Gravity provides the force to keep the moon in its circular orbit

universal

to force of gravity is

projectile motion

the combined horizontal and vertical motion of a launched object

thrown at any speed an object falls 5m after one second, 20m after 2 seconds, etc.

Horizontal

constant speed since no force in that direction

Vertical

accelerated motion since gravity pulls down

the falling path

a projectile falls beneath the imaginary path it would follow if there were no gravity

Angled launch

the object still falls below the imaginary line launch

gravity only affects the vertical component of motion

horizontal and vertical motions

are independent

orbits

direction of motion

at sufficient speed, the falling distance matches the curvature of the Earth

Satellite

if launched fast enough, the projectile will go into orbit and become a

The force of gravity

changes the direction of motion, but NOT the speed

the projectile overshoots a circular orbit

if the launch speed is greater than 8km/s

escape speed

a projectile launched at a sufficiently fast speed will not return to Earth

density

is a measure of how much mass can fit into a given volume

Fixed volume

density is DIRECTLY proportional to mass

fixed mass

density is INDIRECTLY proportional to volume

pressure

a force that acts over an area

measured in units of N/m squared

Small pressure

a force spread over a large area

large pressure

a force spread over a small area

pressure in a liquid

a liquid exerts a force per area

the liquid pressure increases with depth

Liquid pressure

liquid density x gravity x depth

atmospheric pressure

the atmosphere exerts a force on the surface of the earth

Buoyancy force

greater pressure against the bottom than the top of a submerged object produces a net upward force.

density of liquid x volume displaced x gravity

object sinks

if weight is greater than the buoyancy force

object floats

if weight is less than the buoyancy force

object remains at any level

if weight equals the buoyancy force

flotation

BF must be greater than the weight

heavy objects must be built large enough to displace theur weight of fluid

gas pressure

the molecules are more free to move about than in a liquid

gas pressure and density (particles)

if the volume and temperature are held constant and the DENSITY INCREASES, then the PRESSURE WILL INCREASE

gas pressure and volume

if the density of molecules and temperature are held constant and the VOLUME IS DECREASED, the PRESSURE WILL INCREASE

pressure and temperature

if the volume and density of molecules are held constant and the TEMPERATURE IS INCREASED, the PRESSURE WILL INCREASE

Bernoulli’s principle

the spread of a fluid increases in a smaller area

temperature

tells us whether something is hot or cold

a measure of the average kinetic energy of the molecules of a substance

temperature scales

Celsius, Fahrenheit, and kelvin

Boiling temperature

212F 100 C

Freezing temperature

32 F and 0 C

hot

high speed molecules

more thermal energy

fast average speed

cold

low speed molecules

less thermal energy

small average speed

specific heat

the amount of heat needed to change the temperature of 1kg of a substance by 1 degree C

expansion of water

water contracts when cooled until it reaches 40 C

Conduction

transfer of heat by molecular collisions

CONTACT between 2 objects

insulation

slows the transfer of thermal energy

convection

transfer of heat by the movement of a gas or liquid from one position to another

radiation

transfer of heat through space by electromagnetic waves

solid

molecules arranged in a rigid pattern

liquid

molecules constrained, but mobile

gas

molecules unconstrained, move freely

melting

changing a solid to a liquid

freezing

changing a liquid to a solid

boiling/evaporation

changing a liquid to a gas

condensation

changing a gas to a liquid

How do the horizontal and vertical components of a projectile’s motion change?

The horizontal component of a projectile’s motion stays constant because there is no horizontal acceleration. The vertical component changes continuously due to gravity, causing the projectile to slow down as it rises and speed up as it falls.

What would a projectile’s path be if there were no gravity? How far does a projectile fall beneath this path in the presence of gravity?

Without gravity, a projectile would travel in a straight line at constant velocity. With gravity, it falls below that line by a distance proportional to ½ gt squared, where t is the time in motion.

How does the speed of a projectile change during its path? Which components change?

The speed of a projectile changes because its vertical component of velocity changes due to gravity, while the horizontal component stays constant. Only the vertical component changes, causing the overall speed to decrease on the way up and increase on the way down.

How are satellites related to projectiles?

Satellites are essentially projectiles that are launched with enough horizontal speed that, as they fall under gravity, they continuously miss the Earth and stay in orbit. Like projectiles, they have constant horizontal motion and vertical acceleration due to gravity.

How do the properties of circular and elliptical orbits differ?

In a circular orbit, the object moves at a constant speed and stays the same distance from the center at all times. In an elliptical orbit, the distance from the center changes, so the object speeds up when it’s closer and slows down when it’s farther away.

How does the conservation of energy relate to satellite and planet motion?

The conservation of energy means the total energy of a satellite or planet stays constant as it orbits. As it moves closer to the object it orbits, gravitational potential energy decreases and kinetic energy (speed) increases, and as it moves farther away, the opposite happens.

What is meant by the escape speed and what affects its value?

Escape speed is the minimum speed an object needs to completely break free from a planet’s gravity without further propulsion. It depends on the planet’s mass and radius—greater mass increases escape speed, while a larger radius lowers it.

What is the difference between mass, volume, and density?

Mass is the amount of matter in an object, volume is the amount of space it occupies, and density is how much mass is packed into a given volume

How is pressure related to force and area?

Pressure is the amount of force applied per unit area, so P=force over area ​; increasing force increases pressure, while increasing area decreases it.

How does pressure vary with depth in a liquid?

Pressure in a liquid increases with depth because the weight of the liquid above adds more force per unit area

How does a barometer work?

A barometer measures atmospheric pressure by balancing the weight of a column of liquid (usually mercury) against the air pressure. As air pressure increases, it pushes the liquid higher; as air pressure decreases, the liquid falls.

On what properties does the buoyancy force depend?

The buoyant force depends on the volume of the displaced fluid, the density of the fluid, and gravity.

What determines whether an object will float or sink?

Whether an object floats or sinks depends on its density compared to the fluid’s density. If the object’s density is less than the fluid’s, it floats; if it’s greater, it sinks.

How does gas pressure vary with molecular density, temperature, and volume?

Gas pressure increases with molecular density (more molecules per volume) and temperature (faster-moving molecules), and decreases as volume increases (molecules have more space

What is thermal energy?

Thermal energy is the total energy of all the particles in a substance due to their motion and vibrations, which is related to temperature and the amount of matter.

What does temperature measure?

Temperature measures the average kinetic energy of the particles in a substance, indicating how hot or cold it is.

What is absolute zero?

Absolute zero is the lowest possible temperature, 0 K (−273.15 °C), where particles have minimal motion and thermal energy is essentially zero.

What is the definition of heat? What are its units of measurement?

Heat is the transfer of thermal energy from a hotter object to a cooler one. It is measured in calories (cal).

What does the specific heat of a substance measure?

The specific heat of a substance measures the amount of heat needed to raise 1 kilogram (or 1 gram) of the substance by 1 °C (or 1 K). It indicates how resistant a material is to temperature change.

What effect does the specific heat of a substance have on the change in temperature for a given heat input?

A substance with a high specific heat changes temperature more slowly for a given heat input, while a substance with a low specific heat heats up or cools down more quickly.

Do objects expand or shrink when warmed? Cooled?

Objects expand when warmed and shrink when cooled

Why does water expand when it freezes?

Water expands when it freezes because its molecules form ice that takes up more space than in the liquid state.

How is heat transferred via conduction?

Heat is transferred by conduction when thermal energy moves through direct contact between particles, with faster-moving (hotter) particles passing energy to slower-moving (cooler) ones.

What is the difference between good conductors and good insulators?

Good conductors, like metals, transfer heat quickly because their particles or electrons pass energy efficiently. Good insulators, like wood or rubber, slow down heat transfer because their particles do not move energy easily.

How is heat transferred via convection?

Heat is transferred by convection when a fluid (liquid or gas) moves, carrying thermal energy from one place to another

What are examples of heat transfer by conduction, convection and radiation?

• Conduction: A metal spoon getting hot in a pot of boiling water.

• Convection: Warm air rising from a heater and circulating in a room.

• Radiation: Heat from the Sun warming your skin.

What are the properties of the three states of matter?

solid, liquid, gas

How is energy transferred during phase changes?

During phase changes, energy is transferred as heat to break or form intermolecular bonds without changing temperature. For example, heat added melts a solid or vaporizes a liquid, while heat removed freezes or condenses a substance.

Why does evaporation result in cooling?

Evaporation results in cooling because the fastest-moving (hottest) molecules escape from a liquid, leaving behind slower-moving, cooler molecules, which lowers the liquid’s average temperature.

Why does condensation result in warming?

Condensation results in warming because when gas molecules slow down and form a liquid, they release energy into the surroundings, raising the temperature.

How does boiling depend on pressure?

Boiling depends on pressure because a liquid boils when its vapor pressure equals the surrounding pressure. Lower pressure (like at high altitudes) lowers the boiling point, while higher pressure raises it.

Why is boiling a cooling process?

Boiling is a cooling process because the liquid loses its most energetic molecules as they vaporize, which lowers the average kinetic energy and cools the remaining liquid.

According to Newton, the greater the masses of interacting objects, the

greater the gravitational force between them.

According to Newton, the greater the distance between gravitationally interacting objects, the

less the gravitational force between them.