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Unit 05-1 Notes/Output
SPEED: Speed is the change in position (distance) over time. Speed = Distance / Time. We use units to describe
distances such as meters (m), feet (ft), inches (in), centimeters (cm), kilometers (km), etc. The units for time are
minutes (min), seconds (s), and hours (hr). Speed Examples: 2 meters per second (2 m/s), 55 miles per hour (55
mph or mi/hr), or 22 kilometers per hour (22 km/hr).
AVERAGE SPEED: Average Speed is the object’s total distance traveled divided by the total time of travel.
(Average Speed = Total Distance Traveled / Total Time Taken)
CONSTANT SPEED: Constant Speed is when an object in motion neither speeds up nor slows down. The
object’s speed stays the same and does not change, does not accelerate (speed up – positive acceleration), or does
not decelerate (slow down – negative acceleration). (Think cruise control on a car.)
GRAPHING SPEED
This is called a Distance-Time graph, meant for graphing Speed.
Look at the X and Y axis to make sure. When reading a graph: TAILS.
T=Title, A=Look at the Axis, I=Intervals, L=Label the Axis, S=Scale/Legend
There are 4 types of graphs represented here:
1.) A line sloping upward toward the right shows that an object is
travelling at constant speed away from its beginning origin.
2.) A horizontal line shows an object is not moving; it is at rest or
staying still.
3.) A line sloping downward (E) toward the right shows an object is
moving at constant speed toward its beginning origin (0 distance).
4.) A curved line indicates that the object’s speed is either increasing
(getting faster) or decreasing (getting slower) depending on the
direction of the slope.
VELOCITY: Velocity includes the speed of an object AND IT’S DIRECTION. Examples are a racecar traveling
at 55 mph due north, or a hurricane travelling northeast at 10 mph. An object’s velocity can change but its speed
may stay the same. For example, a tornado’s speed stayed the same but it changed direction meaning it changed its
velocity.
ACCELERATION: Acceleration is the change in speed or direction over
time (change in velocity / time). Acceleration increases if a force is applied
in the same direction of the object’s motion. If the force opposes motion (or
goes against the motion), the object will change direction or speed.
Acceleration is graphed in a Velocity-Time Graph (At Right)
INERTIA: Inertia is resistance to a change in an object’s motion. An
outside force (push/pull) is needed to overcome an object’s inertia in order to
change its motion because an object or body at rest tends to stay at rest
unless an outside force causes the object to start moving OR an object or
body in motion tends to stay in motion unless an outside force causes it to
stop moving or causes it to change direction. – Newton’s 1st Law
BALANCED/UNBALANCED FORCES
1. The forces affecting an object are either balanced or unbalanced.
2. A Force equals mass times acceleration (F = ma) – This is Newton’s 2nd Law
3. Balanced forces result in no change to an object’s motion. The two forces are
both equal and opposite.
4. Unbalanced forces are when two forces are not equal; one force is greater than
the other force and causes the object to move in the direction of the greater force.
MOTIONS & FRICTION: Motion is the act of changing position or place.
Examples: moving vehicles, swinging a bat, a ball flying. Examples of forces that affect an object’s motion: a
pushing force, pulling force, friction, gravity, magnetism, and air resistance. Friction is a force that opposes
motion, and slows an object or prevents it from moving. Gravity is a constant, and always accelerates an object at
9.8 m/s2 on Earth. Magnetism is a force with which a magnet is attracted to a metal object.
MASS vs WEIGHT: Mass is NOT affected by gravity because mass is the amount of matter (atoms) that makes up
an object and matter cannot be created or destroyed. Mass is measured in grams (g). Weight is mass affected by the
acceleration of gravity. It is measured in newtons (N). To determine the weight of an object, its mass is multiplied
by 9.8 m/s2. A scale is used to measure weight; a balance is used to measure mass.