Post on 14-Dec-2015
Graphing Speed
• What does a straight line indicate about the speed?
• What does the slope of a line indicate?
• Draw another line showing speed that is changing.
CHECKER AUTO PARTS 500• http://www.nascar
.com/• SPEED = DISTANCE
TIME
DISTANCE = 315 laps
TIME = 3 hours
SPEED = ? Track length = 1 mile
VELOCITY -
• The speed of these racers may not have changed…Explain why their velocity has changed.
• List some examples of how change of direction may be stated:– North, south, east, west
– 280 degrees (on a compass)
– Up, down…
MOMENTUM -
• Momentum = mass x velocity
( p = mv )
How does mass influence momentum?
How does speed influence momentum?
SUMMARY
D IS T A N C E a n d T IM E
S P E E D
S P E E D a n d D IR E C T IO N
V E L O C ITY
V E L O C IT Y a nd M A S S
M O M E N T U M
M O T IO N
ACCELERATION –
ACCELERATION = FINAL VELOCITY – INITIAL VELOCITYTIME
What evidence of acceleration do you see in these pictures?
(read page 260)
boat speeding up
car slowing down
ACCELERATION (continued)
What evidence of acceleration can be seen in this picture?
(changing direction)
ZERO ACCELLERATION -
• Identify two conditions that must be met for these joggers to be at zero acceleration.
(page 261)
1. No change of direction.
2. No change (increase/decrease) in speed.
FORCE –IS THE CAUSE OF ACCELERATION
• Examples of FORCES:– Gravity– Engines– Rubber band–
• BALANCED FORCES do not change motion.
• UNBALANCED FORCES change motion.
FRICTION -
A. SURFACE FRICTION – depends on roughness of surface.
Ways to INCREASE friction:
1. Sandpaper
2.
Ways to DECREASE friction:
1. Oil
2.
FRICTION (continued )B. AIR FRICTION
(resistance) - depends on the size, shape, or speed of an object.Ways to INCREASE friction:1. Larger surface area2. Ways to DECREASE friction:1. Smaller surface area.2.
GRAVITY -
• Gravity is exerted by all objects on each other.
• Depends on mass of objects.– MORE mass = MORE
gravity
• Depends on distance between objects. – MORE distance = LESS
gravity
WEIGHT -
Is the gravitational force an object experiences due to its mass.
Is dependent on ones’ location.
May be described in an equation:
weight = mass x free-fall acceleration( g = 9.8 m/s2 )
The metric unit of measurement is the NEWTON and is measured with a SPRING SCALE.
MASS -Is a measure of the amount of matter in an object.
Is not dependent on location.
The metric unit of measurement is the GRAM and is measured with a BALANCE.
FIRST LAW ( INERTIA) -Objects at rest stay at rest and
objects in motion stay in motion unless an unbalanced force acts on them.
(This law describes what happens when forces on an object are BALANCED and the net force is zero.)
EXAMPLES:
SECOND LAW (ACCELERATION) -
A. This law describes the relationship between force, mass, and acceleration and may be stated as an equation:
force = mass x acceleration ( f = ma )
• (This law describes what happens when forces on an object are UNBALANCED and the net force is not zero.)
B. Acceleration and EQUAL FORCE -
• When the forces are equal, less massive objects accelerate faster than more massive ones.
• EXAMPLES:
C. Acceleration and EQUAL MASS -
• When the masses are equal, a greater force provides greater acceleration.
• EXAMPLES:
FREE FALL -
• When gravity is the accelerating force.
• Acceleration due to gravity is 9.8 m/s/s ( g = 9.8 m/s2 )
• Gravity accelerates all objects at the same rate!
TERMINAL VELOCITY -
• Force of air resistanceequals
the gravitational force (weight)
Object stops acceleratingTerminal velocity for a
human body is about 200 mph.
TERMINAL VELOCITY and AMUSEMENT PARKS
• New ride at Wisconsin Dells – Terminal Velocity.
• 100 foot free fall drop• 70 mph• 140 foot tower• $40 first time…$25
second time
THIRD LAW (ACTION = REACTION)• Every action force has
an equal and opposite reaction force
• F x D = f x d– (action = reaction)
• EXAMPLES:
B A L A N C E D F O R C E S
IN E R T IA
F irs t L aw
U N B A L A N C E D F O R C E S
A C C L E R A T IO N
S e co n d L aw
F O R C E S A C T IN P A IR S
A C T IO N = R E A C T IO N
T h ird L aw
N e w to n s L a w s o f M o tion