Title: MECHANICS
1MOTION
- MECHANICS The branch of Physics that deals with
the motion of objects and the forces that change
this motion.
Kinematics The motion part of Mechanics.
Dynamics The force part of Mechanics.
2POSITION The separation between an object and a
reference point.
DISTANCE (d) The length of the path an object
took as it moved between positions.
SCALAR QUANTITY A measurement with magnitude
but no direction.
SIZE
3DISPLACEMENT (d) The straight line distance and
direction between an objects starting position
and its stopping position.
VECTOR QUANTITY A measurement that has
magnitude and direction. Represented by bold face
variable (text book) or an arrow above the
variable. (Notes)
4PRACTICE
Larry the minion walks 25.0 m, east to visit
Agnus. They then walk 8.0m, west to visit Dr.
Gru. They then all walk 12.0m, east to go to
Krispy Kreme.
L
A
25.0 m
G
8.0 m
12.0 m
A. What is their final position with respect to
Agnus initial position? B. What is Larrys
total displacement? C. What distance did each
person travel?
If Larry now travels back home, what is his
displacement now?
5- SPEED The RATE of distance.
SCALAR
6- VELOCITY The RATE of displacement.
VECTOR
7A soldier marches 18 paces , east in 7 seconds,
stops for 5 seconds and then marches 12 more
paces east in 6 seconds. What is the soldiers
speed and velocity for the whole trip? The
soldier now moves 25 paces, west. If this takes
10.0 more seconds, what is the soldiers speed and
velocity for the whole trip? (From the
beginning)
8Agnus does the following 1m/s for 3 seconds,
then rests for 3 seconds, then 2
m/s for 3 seconds
Larry travels at Agnus average speed
Dr. Gru travels at Agnus average velocity
1m
3m
5m
7m
11m
9m
9Agnus does the following 3m/s for 4 seconds,
then rests for 2 seconds, then -2 m/s
for 4 seconds
Larry travels at Agnus average speed
Dr. Gru travels at Agnus average velocity
1m
3m
5m
7m
11m
9m
10- 1. A swimmer dives into a pool and swims 50.0 m,
east in 8.00 seconds and then turns around and
swims 30.0 m west in 5.00 seconds. - A. What is the average speed of the swimmer?
- B. What is the average velocity of the swimmer?
50.0 m
30.0 m
11- Warm-up. A car travels 100 miles, east in 5.0
hours, then travels 75 miles, west in another 5
hours and then does one more thing that takes 5
more hours. If the cars average velocity for
the whole trip is 25 miles/hour, east, what
displacement did the car have in the third part
of the trip?
12Acceleration The RATE of velocity change.
GALILEO when an object gains or loses equal
increments of speed during equal increments of
time.
UNITS?
m
s
2
s
t time required for the velocity change
VECTOR
13Concept Review 1. What does it mean if an
object has a positive acceleration? 2. What does
it mean if an object has a negative
acceleration? 3. What does it mean if an object
has zero acceleration? 4. Is it possible for an
object to have zero velocity and a non-zero
acceleration? Explain. 5. How are velocity and
acceleration related?
14Concept Review 2 1. Describe the motion of an
object that has an acceleration of 5 m/s2,
north? 2. Describe the motion of an object that
has an acceleration of 2 m/s2, east and an
initial velocity of 10 m/s, west. 3. Describe
the motion of an object that has a 0 m/s2? 4.
What would be the velocities each second for the
next 10 seconds for an object that has vi 10
m/s west and a 3 m/s2, east? Describe what this
motion would look like. 5. How are velocity and
acceleration related?
15ACCELERATION PRACTICE 1. A sprinter in the 100
m dash is at full speed by the 20.0 m mark. If
the velocity of the sprinter is 15.0 m/s, east by
the 20.0 m mark, and if it takes 3.2 seconds to
get to this mark, what is the acceleration of the
sprinter through the first 20.0 meters of the
race? (Hint What is the sprinters initial
velocity?)
16- 2. A car accelerates at 7.0 m/s2, North for 8.0
seconds. What is the final velocity of the car
if its initial velocity is - 0.0 m/s?
- 10.0 m/s, North?
- 7.o m/s, South?
- For problem 2, what would the answers be if the
acceleration was 7.0 m/s2, South? -
17- 3. How long would it take a train to go from a
velocity of 6.0 m/s, East, to 123 m/s, East if
its acceleration is 2.73 m/s2, East?