Chapter 2 Motion
2-8. Mass2-9. Second Law of Motion2-10. Mass and Weight2-11. Third Law of Motion 2-12. Circular Motion2-13. Newton's Law of Gravity2-14. Artificial Satellites
2-1. Speed 2-2. Vectors2-3. Acceleration2-4. Distance, Time, and Acceleration 2-5. Free Fall System2-6. Air Resistance2-7. First Law of Motion
2-1. Speed• Definitions:
– Speed• The rate at which something moves a given distance.
• Faster speeds = greater distances
– General formula for speed:• Speed = distance / time
• Abbreviations commonly used:d = distance t = time v = speed
v = d/t
2-1. Speed
mphhour
miles
hours
miles
t
dv 4040
5.2
100
mileshourshour
milestvd 180630
hourshourmiles
miles
hourmiles
miles
v
dt 5.2
/5.2
/40
100
Velocity
Distance
Time
2-1. Speed
Average speed is the total distance traveled by an object divided by the time taken to travel that distance.
Instantaneous speed is an object's speed at a given instant of time.
2-2. Vectors
Velocity is a vector quantity that includes both speed and direction.
2-3. Acceleration
Acceleration of an object is the rate of change of its velocity and is a vector quantity. For straight-line motion, average acceleration is the rate of change of speed:
interval time
speedin changeonAccelerati
t
vva
if
2-3. Acceleration
3 Types of Acceleartion
Speeding Up
Slowing Down
Turning
2- 4. Distance, Time and Acceleration
(V1 + V2) Vavg =
2
d = vavg t
d = ½at2
(20mph + 60mph) = 40mph 2
30mph 2hr = 60miles
½ 10m/s/s 52 = 125m
2-5. Free Fall
The acceleration of gravity (g) for objects in free fall at the earth's surface is 9.8 m/s2.
Galileo found that all things fall at the same rate.
2-5. Free Fall
The rate of falling increases by 9.8 m/s every second.
Height = ½ gt2
For example:
½ (9.8 )12 = 4.9 m
½(9.8)22 = 19.6 m
½ (9.8)32 = 44.1 m
½ (9.8)42 = 78.4 m
2-5. Free Fall
A ball thrown horizontally
will fall at the same rate as a ball dropped
directly.
2-5. Free Fall
A ball thrown into the air will slow down, stop,
and then begin to fall with the acceleration
due to gravity. When it passes the thrower, it will be traveling at the same rate at which it
was thrown.
2-5. Free Fall
An object thrown upward at an angle to the ground follows a curved path called
a parabola.
2-6. Air Resistance
• In air…– A stone falls faster
than a feather• Air resistance
affects stone less
• In a vacuum– A stone and a
feather will fall at the same speed.
2-6. Air Resistance
• Free Fall– A person in free
fall reaches a terminal velocity of around 54 m/s
– With a parachute, terminal velocity is only 6.3 m/s
• Allows a safe landing
2-6. Air Resistance
• Ideal angle for a projectile– In a vacuum, maximum distance is at an angle of 45o
– With air resistance (real world), angle is less• Baseball will go furthest hit at an angle of around 40o