Chapter 2 Motion 2-8. Mass 2-9. Second Law of Motion 2-10. Mass and Weight 2-11. Third Law of Motion 2-12. Circular Motion 2-13. Newton's Law of Gravity.

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