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Motion, Force and Gravity
Chapter 2.1, 2.1 2.3, and 2.5
42
Science
8th Grade
05/07/2013

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Cards

Term
Newton's First Law
Definition

An object at rest will remain at rest,

and an object moving at a constant velocity will continue moving at a constant velocity

unless acted upon by an unbalanced force

Term
Inertia
Definition
the tendency to resist change in motion
Term
Inertia depends on.....
Definition
Mass
Term
Newton's 2nd Law
Definition

Acceleration depends on the object's mass

and on the net force acting on the object.

Term
Acceleration formula
Definition

Acceleration = Net force

                    Mass     

Term
Force net formula
Definition
Force = Mass x Acceleration
Term
2 ways to increase acceleration
Definition

Decrease mass 

or

Increase force

Term

What allows a rocket

to lift off?

Definition
Gases expelled exert an equal but opposite reaction force
Term
Satelite
Definition

an object that orbits

another object

Term
Centripetal force
Definition

a force that causes objects to move in a circle

("center seeking")

Term
Satelite motion
Definition

velocity is straight forward, but gravity bends the direction

 

Term
Why are satelites falling?
Definition
Satelites are falling, but because the earth is round, the satelites continually fall around the curved earth.
Term
Definition of 1 Newton
Definition
1 N = the force required to give a 1-kg mass an acceleration of 1 m/s2
Term
Definition of force
Definition
a push or a pull
Term
Newton
Definition
the SI unit for force
Term
Net force
Definition

the combination of all forces acting on an object at one time 

(determines movement)

Term
unbalanced forces
Definition
cause a change in movement (start or stop, faster or slower, or change in direction)
Term
balanced forces
Definition

result in no change in motion; 

cancel out

Term
Friction
Definition
the force of 2 surfaces on each other
Term
Friction depends on what 2 factors?
Definition

the type of surface (rough or smooth)

and how hard the surfaces are pushed together

Term
static friction
Definition
The friction force that makes it hard to get things to start o move
Term
Sliding Friction
Definition
2 surfaces sliding together
Term
Rolling friction
Definition

ball bearings

(easy to overcome)

Term
Fluid Friction
Definition
the force on an object moving through a fluid such as air, water, or oil
Term
Force arrows can show what two things?
Definition
strength and direction of a force
Term
How can arrows show net force?
Definition
Forces in the same direction add together.  Forces in opposite directions subtract to form a net force
Term
What happens to a moving object that has no friction?
Definition

It keeps moving forever

or until it encounters a force that changes its motion

Term
Gravity
Definition
a force that pulls (all) objects toward each other
Term
9.81 m/s2
Definition

rate of acceleration due to gravity on all objects

(no matter what mass)

Term
Universal Law of Gravitation
Definition
The the force of gravity that exists between ALL objects
Term
Factors affecting gravity
Definition
Mass of the objects and their distance apart
Term
Mass
Definition
the amount of matter in an object
Term
Weight
Definition
A measure of the amount of gravitational force on an object
Term
Free fall
Definition
when the only force acting on an object is gravity
Term
Air resistance
Definition
a type of fluid friction
Term
In what direction is friction?
Definition
In the opposite direction of the motion of the object
Term
Terminal Velocity
Definition
Reached when air resistance equals the weight of an object.  It then accelerates no further, keeping the same speed
Term
Projectile
Definition
an object that is thrown
Term
In no air (a vacuum) how do objects of different sizes or masses accelerate due to gravity.
Definition

at the same rate 

(They hit ground at the same time)

Term
In air, how do objects of different sizes accelerate due to gravity?
Definition

More surface area (larger object) slows acceleration. 

These objects will hit the ground at different times in air.

Term
If one object is dropped and, at the same exact time, another identical object is thrown, which object will reach the ground first?
Definition
They will reach the ground at the same time.
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