Forces, 8Th Grade Science, Unit 5

Front 1

a push or pull

Back 1

force

Front 2

A force is described by its

Back 2

magnitude and the direction in which it acts

Front 3

Arrows are often used to represent the direction and _______ of a force.

Back 3

strength

Front 4

The SI unit for magnitude, or strength, or a force is the ____________

Back 4

newton (N)

Front 5

One newton (N) of force is equal to about the strength it takes to lift up an _________.

Back 5

apple

Front 6

The combination of all forces acting on an object is called the ___ _______.

Back 6

net force

Front 7

When two or more forces act in the same direction, the net force is found by _________ the forces together.

Back 7

adding

Front 8

When two forces act in opposite directions to each other, one is a positive force and one is a _____ force.

Back 8

negative

Front 9

If the opposing forces are of equal strength, the net force is ___.

Back 9

zero

Front 10

_______ forces acting on an object result in a net force and cause a change in the object's velocity.

Back 10

Unbalanced

Front 11

Equal forces that act on one object in opposite directions are called _____

Back 11

balanced forces

Front 12

Balanced forces acting on an object do not change the object's _____.

Back 12

velocity

Front 13

A force that two surfaces exert on each other when they rub against each other.

Back 13

friction

Front 14

Without friction, a moving object will not _____ until it strikes another object.

Back 14

stop

Front 15

Does a smooth surface produce more or less friction than a rough surface?

Back 15

less

Front 16

The strength of the force of friction depends on the ______ of surfaces involved and how _______ they push together.

Back 16

type
hard

Front 17

Friction that acts on objects that are not moving is called ____ ______.

Back 17

static friction

Front 18

When two solid surfaces slide over each other.

Back 18

sliding friction

Front 19

If an object is pulled across a surface, this would be an example of what typd of friction?

Back 19

sliding friction

Front 20

When an object rolls across a surface.

Back 20

Rolling friction

Front 21

Skates, skateboards, and bikes are all examples of objects that utilize what type of friction?

Back 21

rolling friction

Front 22

When a solid object moves through a liquid, this is called what type of friction?

Back 22

fluid friction

Front 23

We put oil in machines to help to create _______ friction instead of sliding friction.

Back 23

fluid

Front 24

A force that pulls objects toward each other.

Back 24

gravity

Front 25

Where does gravity take place?

Back 25

everywhere

Front 26

The statement that "the force of gravity acts between all objects in the universe" is known as ____.

Back 26

The Universal Law of Gravitation

Front 27

The force of gravity between objects _____ with greater mass and ______ with greater distance.

Back 27

increases
decreases

Front 28

The amount of matter in an object is known as its ______.

Back 28

mass

Front 29

The SI unit of mass is the _____.

Back 29

kilogram

Front 30

The force that causes the planets to stay in orbit around the sun is _____.

Back 30

gravity

Front 31

The gravitation force exerted on a person or object at the surface of a planet is known as _____.

Back 31

weight

Front 32

The formula for calculating the weight of an object is:

Back 32

weight = mass x acceleration due to
gravity

Front 33

When the only force acting on an object is gravity, the object is said to be in ____ _____.

Back 33

free fall

Front 34

The force of gravity alone causes an object to accelerate in what direction?

Back 34

downward

Front 35

Objects fall with an increasing speed of _______ meters/second

Back 35

9.8

Front 36

A type of fluid friction that acts on objects falling through the air.

Back 36

Air resistance

Front 37

What causes a flat piece of paper to fall slower than a crumpled piece of paper?

Back 37

Air resistance

Front 38

An object that is thrown

Back 38

projectile

Front 39

Matter is considered to be _____ if it returns to its original shape after it is squeezed or stretched.

Back 39

elastic

Front 40

Compression and tension are two types of ______ forces.

Back 40

elastic

Front 41

An elastic forces that squeezes or pushes matter together.

Back 41

compression

Front 42

An elastic force that stretches or pulls matter.

Back 42

tension

Front 43

A shoe hanging from a line on a fishing pole is demonstrating the force of _____.

Back 43

tension

Front 44

The statement that an object will remain at rest or moving at a constant velocity unless it is acted upon by an unbalanced force is known as____

Back 44

Newton's First Law of Motion

Front 45

The tendency of an object to resist a change in motion.

Back 45

intertia

Front 46

When a car stops, _____ keeps you moving forward.

Back 46

inertia

Front 47

The greater the mass of an object, the _______ its inertia.

Back 47

greater

Front 48

The statement that acceleration depends on the net force acting on the object and on the object's mass is known as ___.

Back 48

Newton's Second Law of Motion

Front 49

The formula for acceleration is:

Back 49

Acceleration = net force / mass

Front 50

The statement that "if one object exerts force on another object, the second object exerts a force of equal strength in the opposite direction on the first object" is known as ___.

Back 50

Newton's Third Law of Motion

Front 51

For every action, there is an equal but opposing _____.

Back 51

reaction

Front 52

When you jump up, you push on the ground, and the ground pushes back. This is known as what type of pair?

Back 52

action-reaction

Front 53

Do action-reaction pairs cancel each other out? Why?

Back 53

No, because they are acting on different objects.

Front 54

The quantity of motion is known as

Back 54

momentum

Front 55

The formula for calculating momentum is:

Back 55

momentum = mass x velocity

Front 56

The more momentun an object has, the harder it is to change its ____.

Back 56

velocity

Front 57

The total amount of momentum objects have is ______ when they collide.

Back 57

conserved

Front 58

In the absence of outside forces, the total momentum of objects that interact does not change. This is known as:

Back 58

The law of conservation of momentum

Front 59

If two moving objects collide, the momentum of one object decreases, while the the momentum of the other object ______.

Back 59

increases

Front 60

If a moving object hits a stationary object, all of the momentum of the moving object is ______ to the non moving object.

Back 60

transferred

Front 61

A rocket can rise into the air because the gases it expels with a ______ ____ force exerting an equal but ____ _____ force on the rocket.

Back 61

downward action
opposite reaction

Front 62

An object that orbits another object in space.

Back 62

satellite

Front 63

Any force that causes an object to move in a circular path.

Back 63

centripetal force

Front 64

Centripetal force means _____ _____.

Back 64

center seeking

Front 65

The faster you throw an object, the ____ it travels before it lands.

Back 65

farther

Front 66

Satellites in orbit around Earth continuously _____ toward Earth, but because Earth is _____ they travel around it.

Back 66

fall
curved

Front 67

The name of the man credited with much of our knowledge of forces.

Back 67

Sir Isaac Newton