# Force.Motion.NOTES ```FORCE AND MOTION
Study Notes
FORCE: a push or pull acting on an object.
examples of forces are gravity, friction, magnetism, and applied
forces.
Forces cause an object to change its speed, direction, or both.
Applied force: is force that a person or thing applies to another
object.
There are BALANCED and UNBALANCED Forces:
 Balanced forces are forces acting on an object from opposite
directions that are equal. These objects with balanced forces
acting upon them will most likely be STILL – Not Moving.

Unbalanced forces are forces acting on an object from opposite
directions that are not equal. These objects with unbalanced
forces acting upon them are in MOTION - MOVING.
The Tug-Of-War in the top image is a “draw” – no one is winning
or losing – BALANCED FORCES
The Tug-Of-War in the bottom image shows the Left side
winning because they have more force than the right side –
UNBALANCED FORCES
INERTIA: is the “stubbornness” of an object to a) stay at rest, b)
stay in motion, or c) stay moving in one direction.
Law: Nothing moves from sitting, stops from moving, or
changes direction without an outside force acting on it.
(Newton’s 1st Law of Motion; “Law of Inertia”)
GRAVITY: is the force that pulls everything toward the center of
the earth.
In the Catapult Lab we conducted, we flung objects of different
masses but applied the same strength of force by pulling back the
spoon the same for each clay object.
And we found that objects of small mass were less affected by
Gravity and that allowed those to fly faster and further than objects
with greater mass. The greater the mass, the more gravity (and air
resistance – a type of friction) affected their speed and distance –
the greater the mass, the slower and they flew and the closer they
landed.
GRAVITY affects objects being thrown in the air – and the
relationship with the object and the ground is affected by the gravity
and mass of the object:
FRICTION: is a force that works against motion; the action of one
surface or object rubbing against another surface or object. Friction
stops or slows down moving objects. Friction can help moving
objects change direction.
Air Resistance is a type of friction. It slows things down that
are moving through the air (cars, thrown objects, falling objects).
MOMENTUM: officially, momentum is the amount of mass an object has
multiplied by its velocity. Mass x Velocity
For 5th grade purpose, let’s just say that MOMENTUM is the force of
energy an object has when it is moving.
 You need to know that the larger the mass of an object in motion,
the more momentum it will have than objects with smaller mass.
But only true if the velocities of the two objects are similar.
 And, similarly, the more velocity an object has in motion, the more
momentum it will have than objects with less velocity. But only true
if the mass of the two objects are similar.
If a baseball is thrown and travels at 55 mph,
And a large truck is also traveling at 55 mph,
….the truck with much more mass will have much more
MOMENTUM….and it will take much more energy to stop the truck than
it will to stop the baseball.
An object in motion has INERTIA – it’s moving and wants to
continue moving! And it has MOMENTUM (force is needed
against its movement to stop the object). The larger the mass,
the harder it is to stop it because it will have more momentum
than a lighter object.
SPEED: calculated by this:
Distance divided by time
SPEED = distance / time
SPEED = distance &divide; time
A familiar example is the speed of a car. In the U.S., this is usually expressed in miles per
hour. Think about a trip you and your family made in the car. Maybe the trip covered 120 miles
and it took 3 hours. What was the car’s average speed?
Speed = distance / time
Speed = 120 miles / 3 hours = 40 mph
On the basketball court we walked fast from start to finish and most of you walked an average of 88
feet in 11 seconds.
So, to calculate the speed, we plug in the numbers to the SPEED FORMULA:
SPEED = distance / time
SPEED = 88 feet / 11 seconds = 88 &divide; 11 = 8! But you need to include a label with that number 8 …..
well, we walked 88 feet in 11 seconds, so the feet and the seconds are part of the label. If we walked
88 feet in 11 seconds, then we walked 8 feet in 1 second, right?
We use the word “per” to mean “in one”…..8 feet per second = 8 feet in one second
SO……. SPEED = 88 feet / 11 seconds = 88 &divide; 11 = 8 feet per second, or 8 ft/sec
ALSO – You need to know how to calculate DISTANCE when given Time and Speed:
Just like
50 = 100 &divide; 2
2 x 50 = 100
Speed = Distance &divide; Time
Time x Speed = Distance
So, if you’re given the Speed and Time, then you can calculate the Distance traveled!
Examples:
If you travel for 1 hour at 30 mph (miles per hour)…then you traveled 30 miles!
Because…1 hour x 30 = 30
If you travel for 2 hours at 30 mph….then you traveled 60 miles!
Because…2 hours x 30 = 60
If you travel for 3 hours at 40 mph = 3 x 40 = 120 miles you traveled!
GRAPHING
Graphing Distance and Time
We spent time looking at numerous graphs and matching them with
stories and tables of data.
We found that the appearance or shape of the graph does NOT represent
the shape of the path or ground.
(in red – there are 3 LINE SEGMENTS above)
Like in this graph above….
We found that the “up and down” of the line on the graph indicates the
DISTANCE from home – the higher the coordinate, the further away from
home. When the coordinate is on the bottom line, then the traveler is
“home.”
We found that the steeper the line segment, the faster the speed. If the
line segment is closer to a straight line, that means the traveler is going
slower. If the line segment is a straight line, then the traveler has
completely stopped.
```