Chapter 2a Motion. 2-1. Speed 2-2. Vectors 2-3. Acceleration 2-4. Distance, Time, and Acceleration 2-5. Free Fall System 2-6. Air Resistance. 2-1. Speed. Definitions: Speed The rate at which something moves a given distance. Faster speeds = greater distances General formula for speed:
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2-4. Distance, Time, and Acceleration 2-5. Free Fall System2-6. Air Resistance
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.
Magnitude of a quantity tells how large the quantity is.
Scalar quantities have magnitude only.
Vector quantities have both magnitude and direction.
Velocity is a vector quantity that includes both speed and direction.
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:
3 Types of Acceleartion
(V1 + V2) Vavg = 2
(20mph + 60mph) = 40mph 2
d = vavg t
d = ½at2
30mph 2hr = 60miles
½ 10m/s/s 52 = 125m
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.
The Slinky Experiment
Super Slinky Experiment
The rate of falling increases by 9.8 m/s every second.
Height = ½ gt2
½ (9.8 )12 = 4.9 m½(9.8)22 = 19.6 m
½ (9.8)32 = 44.1 m
½ (9.8)42 = 78.4 m
A ball thrown horizontally will fall at the same rate as a ball dropped directly.
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.
An object thrown upward at an angle to the ground follows a curved path called a parabola.
2-7. First Law of Motion
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
2-14. Artificial Satellites
The first law of motion states: If no net force acts on it, an object at rest remains at rest and an object in motion remains in motion at a constant velocity.
Inertia keeps a pendulum swinging in the same direction regardless of the motion of the earth. This can be used to measure the motion of the earth. As the Foucault Pendulum swings it appears to be rotating, but it is the earth that is rotating under it. To the right is the Foucault Pendulum at the Pantheon in Paris, France.
Other Web sites that illustrate the Foucault Pendulum.
Inertia is the apparent resistance an object offers to any change in its state of rest or motion.
Newton's second law of motion states: The net force on an object equals the product of the mass and the acceleration of the object. The direction of the force is the same as that of the acceleration.
F = Ma
A force is any influence that can cause an object to be accelerated.
The pound (lb) is the unit of force in the British system of measurement:
1 lb = 4.45 N (1 N = 0.225 lb)
The third law of motion states: When one object exerts a force on a second object, the second object exerts an equal force in the opposite direction on the first object.
Examples of the 3rd Law
Centripetal force is the inward force exerted on an object to keep it moving in a curved path.
Centrifugal force is the outward force exerted on the object that makes it want to fly off into space.
833 N is needed to make this turn.
If he goes too fast, which wheels are likely to come off the ground first?
G = 6.67 x 10-11 N•m/kg2
GPS-Global Positioning Satellite