Transcript CH11 Notes - Moline High School

Chapter 11
Motion
Motion
 Motion- Change in position when
compared to a reference point or frame of
reference
 Reference Point - stationary (non-moving)
object
Measurements of motion:
 Distance – how far you traveled.
 Distance measures the path taken.
 Measure the length of the path. Usually
we measure in meters.
- Displacement – the change of an objects
position.
Speed
 Speed - Distance traveled divided by the
time it took to move that distance.
- constant speed – speed that does not change.
-average speed – total distance divided by total
time
equation to find speed:
 Speed = Distance / Time
Velocity
 Velocity - measurement that describes
both speed and direction.
- equation to find velocity:
velocity(v) = distance/time and
direction
Velocity
ex. The swimmer swam 110m
towards the shore in 72 sec. What
is the swimmers velocity?
Try it!
 Determine which are measurements of
speed and which are measurements of
velocity:
a. 6 mi/hr
b. 3 m/sec N
c. 16 km/h down the street
d. 9 km/h
Acceleration
 Acceleration - change in velocity during a
time interval.
* any change in velocity causes
a change in acceleration!
Acceleration
- increasing velocity = positive
acceleration
- decreasing velocity = negative
acceleration (deceleration)
Acceleration Equation
- equation to find acceleration:
final velocity - initial velocity
change in time
Acceleration
 Ex. Flowerpot falls off a ledge. It hits the
ground in 1.5 sec. w/a velocity of 14.7
m/sec. Find the acceleration.
Different arrangements of the
acceleration equation:
t = vf – vi
a

- time:

- final velocity: vf= at +vi

- initial velocity:
vi= vf - at
Forces
 Force – Any push or pull that can cause a change
in motion.
 4 Fundamental Forces:

- gravity

- electromagnetic force

- strong nuclear force

- weak nuclear force
 Net force – all the forces acting on an
object
Balanced forces – net force equal to zero
- no change in motion
Unbalanced forces – net forces does not equal
zero
- change in motion
Friction
 Friction - a force between two objects in
contact with each other.
 Usually oppose the motion of objects
 Can be both negative and positive
-reduce friction: by adding a barrier between the
two surfaces. Ex. Oil, grease, water
Two types of friction:
 Static friction - The force that resists the beginning
change in motion
 Kinetic friction - The force that opposes the
movement of the two objects
moving over each other
Kinetic Friction
There are three types of kinetic friction
1. Sliding friction When 2 objects slide over each other
-two factors that affect sliding friction
- mass
-surface texture
Ex. Walking, sliding, skiing
2. Fluid friction When matter flows over an object
slowing it down
Ex. Airplane, frisbee, rowing a boat
3. Rolling friction When two objects roll over each other
-less friction with rolling because there is less
surface area touching
Ex. Roller skating, ball rolling on
floor