RISE Science Grade 7 flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Net force

The single force that results from combining all forces acting on an object. It determines whether the object's motion changes; a net force of zero means motion stays the same.

Balanced forces

Forces acting on an object that are equal in size and opposite in direction. They cancel out, so the object stays at rest or keeps moving at constant velocity.

Unbalanced forces

Forces that do not cancel because they differ in size or direction. A nonzero net force makes an object speed up, slow down, or change direction.

Newton's second law

The acceleration of an object equals the net force acting on it divided by its mass, written F = m × a. A larger force or a smaller mass produces greater acceleration.

Newton's third law

For every action force on one object there is an equal and opposite reaction force on a different object. Because the forces act on different objects, they do not cancel.

Inertia

The tendency of an object to resist any change in its motion. Objects with greater mass have greater inertia, so more force is needed to accelerate them.

Gravity

A noncontact force of attraction between any objects that have mass. Near Earth's surface it pulls objects downward with an acceleration of about 9.8 m/s².

Friction

A contact force that opposes motion between surfaces that are touching. It converts motion energy into thermal energy, slowly bringing moving objects to a stop.

Mass and weight

Mass is the amount of matter in an object, measured in kilograms. Weight is the gravitational force pulling on that mass, measured in newtons and equal to mass times 9.8.

Speed and velocity

Speed is the distance an object travels per unit of time, such as meters per second. Velocity is speed combined with a direction, so turning changes velocity.

Magnetic poles

Regions of a magnet where magnetic force is strongest. Like poles repel each other, opposite poles attract, and the force acts without the magnets touching.

Plate tectonics

The theory that Earth's rigid outer shell is broken into plates that move slowly over the hotter, flowing mantle. Their motion builds mountains and causes earthquakes and volcanoes.

Divergent boundary

A plate boundary where two plates move apart. Magma rises to fill the gap, forming new ocean crust at mid-ocean ridges or a rift valley on land.

Convergent boundary

A plate boundary where two plates collide. One plate may sink beneath the other, producing deep ocean trenches, volcanic mountain ranges, and earthquakes.

Transform boundary

A plate boundary where two plates slide past each other horizontally. Crust is neither created nor destroyed, and the grinding motion causes earthquakes along faults.

Subduction

The process in which a denser oceanic plate sinks beneath a less dense plate into the mantle. It creates deep trenches and supplies magma for volcanic eruptions.

Earthquake epicenter

The point on Earth's surface directly above the focus, the underground origin of an earthquake. Shaking is usually strongest at and near this surface point.

Law of superposition

In undisturbed sedimentary rock layers, the oldest layer lies at the bottom and the youngest at the top. Scientists use this rule to order events in Earth's history.

Index fossil

A fossil from a species that lived only briefly but was widespread geographically. Its presence helps scientists match and date rock layers in different places.

Weathering erosion deposition

Weathering breaks rock into smaller pieces, erosion moves those pieces away, and deposition drops them in a new location, building new landforms and sedimentary layers.

Uniformitarianism

The principle that the same natural processes seen today, such as erosion, deposition, and volcanism, also operated in the past. It lets scientists explain ancient rocks using present processes.

Earth's layers

Earth's interior consists of a thin rocky crust, a hot slowly flowing mantle, a liquid metal outer core, and a solid metal inner core, with heat increasing toward the center.

Cell theory

The accepted idea that all living things are made of one or more cells, the cell is the basic unit of structure and function, and new cells come from existing cells.

Cell membrane

A thin flexible barrier surrounding a cell that controls which materials enter and leave. It lets nutrients in and wastes out while keeping the cell's contents inside.

Nucleus

The membrane-bound organelle that contains a cell's DNA and directs most of its activities, including growth and reproduction. Plant and animal cells both have one.

Mitochondria

Organelles that release energy stored in food through cellular respiration. Cells needing lots of energy, such as muscle cells, contain especially many of them.

Chloroplast

A green organelle found in plant cells that captures sunlight and uses it with water and carbon dioxide to make sugar during photosynthesis, releasing oxygen as a product.

Cell wall

A rigid outer layer surrounding plant cells that provides support and shape. Animal cells do not have one, which is a key difference between the two cell types.

Levels of organization

In multicellular organisms, cells form tissues, tissues form organs, organs form organ systems, and organ systems work together to make up the whole organism.

Structure and function

The principle that the shape of a body part or cell matches the job it performs. For example, flat disc-shaped red blood cells carry oxygen efficiently through narrow vessels.

Photosynthesis

The process in which plants use sunlight, water, and carbon dioxide to make sugar and release oxygen. It takes place mainly in the chloroplasts of leaf cells.

Homeostasis

The ability of an organism to keep internal conditions, such as body temperature, water balance, and blood sugar, steady even when the outside environment changes.