Chapter 2 Notes
Overview: basic concepts in physics.
Description
Position (location of an object and the time it takes)
Velocity
Acceleration
Applications
Horizontal motion on land
Falling objects
(2D motion)
Explanations
Forces
Newton’s Laws
Applications
Momentum
Circular motion
Newton’s law of gravitation
Measuring Motion
Measured by change in position and time. (e.g. ball)
•
Speed (distance/time… change in distance divided by change in time, ratio
of distance over time)
•
Change in position with respect to time
•
Speed = distance/time
•
Instantaneous speed – time interval approaches zero,
the numbers so small they appear to happen instantaneously
•
V is used for both speed and velocity
•
v (with a
bar over the v) = d/t
•
speed is a scalar, because it does not have a destination
•
Velocity (distance/time + direction) must have a direction.
•
Velocity is a vector, it has a direction
•
Velocity is the distance traveled per unit time in a given direction,
making it a vector quantity
•
Acceleration (Velocity/time)
Problem: the driver of a car moving at 72.0 km/hr drops a road map. How far (in meters) did the
driver travel if it takes him 3 s to retrieve the map?
Given:
72 km/hr
3 s
V= D/t (rearrange to) D=Vt
Convert V from km/hr to m/s. 72km/hr = 20m/s
D = 60m
Acceleration
It is change in velocity over change in time. (delta V/delta t). Delta always implies final
minus initial.
What is the acc. of a bicycle that moves from rest to 5m/s in 5s?
A = deltaV/deltat
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A = 50/5
A = 1m/s^2
Forces
Force is the push and pull that changes the motion of an object.
Aristotle reasoned that: when you drop two objects, the heaviest one will hit the ground
first. Also, he thought that when there is horizontal motion, one needs a force to act. He
believed that force is required for a uniform horizontal motion.
Galileo and Newton experimentally showed that all objects fall at the same rate and no
force is required for uniform horizontal motion.
Horizontal motion does not change, but the vertical can (a parabola)
Net Force
Friction and Air Resistance and Gravity and Push and Pull all added together acting on an
object. The object will move in the direction of the net force. If all forces are equal, the
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 Spring '08
 McQUIDDY
 Business, Force, horizontal motion, Strong Radioactive Force Gravitational Force

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