Transcript Speed/Motion Notes!

Speed/Motion Notes!
• Motion – an object is in motion if it changes
position to a reference point
• r=d/t
• Constant speed g speed does not change
• Average speed g speed changing
(total distance/total time)
• Instantaneous speed g the speed of an
object at any given instant
0.31
0.85
0.97
1.06
1.53
1.95
2.47
2.71
3.54
3.89
4.03
4.55
4.78
5.28
5.91
6.44
6.79
7.03
7.67
What is the average speed of
this bowling ball?
S=d/t
S=19m/7.67sec
S=2.48m/sec
Distance vs. Time
Distance (meters)
distance time
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
15
10
5
0
0
1
2
3
4
5
Time (sec)
6
7
8
9
Slope and Speed
Distance (m)
Distance vs Time
Which trial has the
greatest slope?
40
30
20
10
0
Trial 1
Trial 2
Trial 3
0
5
Time (sec)
10
Which trial travels the
farthest in the 10
seconds?
Which trial has the
fastest speed?
Slope = y/x = distance/time = Speed
 Is short for “change in”
SLOPE = SPEED!!!!!!
• Time=
• Distance=
distance/speed
speed*time
• A lion runs at 50mph
for .5 hr. How far
does he travel?
• d=r*t
• d=50 mi/hr*.5hr
• d=25 mi
• An elephant runs at
25mph for 50 mi.
How long does it
take to get where he
is going?
• t=d/r
• t=50mi/ 25mi/hr
• t=2 hr
A hyena travels for 30 mi. for .75 hr. How
fast is the hyena traveling?
r=d/t
r= 30mi./.75hr
r= 40 mi./hr
Velocity
• Velocity g
speed and direction!
o
•Boat a 6 mph east
•River c 4 mph east
•Velocity=6 mph east+ 4mph east
•V= 10 mph east
•River b 4mph west
•Velocity=6mph east– 4mph west
•V= 2mph east
Ferris Wheel
The speed is constant but it is always
changing velocity because it is always
changing direction!
http://www.ies.co.jp/math/java/trig/kanran/kanran.html ferris
wheel
Acceleration
The rate at which velocity changes.
This can be an increase in velocity (acceleration)
This can be a decrease in velocity (deceleration or
negative acceleration)
A=(final velocity-initial velocity)/time
A=(Vf-Vi)/t
What is the acceleration of a car that goes from 0 to
60mi/hr in 10 sec.?
A=(vf-vi)/t
A= (60mi/hr)/10 sec.
A=6 mi/hr/sec.
What is the acceleration of a car that slows down
from 70mi/hr to 25 mi/hr in 15 sec.?
A=(vf-vi)/t
A=(25mi/hr-70mi/hr)/15 sec.
A=-45mi/hr/15sec. A=-3mi/hr/sec
A roller coaster is
constantly
accelerating
because the velocity
is always changing!
What is the acceleration of a roller coaster that starts
with a velocity of 4 m/s and accelerates to 22m/s in 3
sec.?
A=(22m/s-4m/s)/3s
A=18m/s//3s
A=6m/s/s or 6m/s2
Gravity!
Gravity: a force that pulls objects together.
Freefall: a falling object with no other force but gravity acting
upon it.
Acceleration due to gravity is 9.8m/s/s
The person jumps off
the plane.
What is his speed at
1 sec?
2 sec?
3 sec?
Terminal Velocity!
The maximum velocity a falling object can achieve.
The air resistance equals the force of gravity so the
object does not accelerate any more.
http://hypertextbook.com/facts/JianHuang.shtml