Ch. 2 Information for Test- Physics
Define average velocity.
- the change in position of the object moving along a straight line, divided by the time during which the change occurred - the equation is the change in the position/ time interval
Give examples of the four types of motion.
1. *Straight Line*- a bowling ball rolling in a gutter; a train on a straightway; a drag-racing car; an object falling straight down 2. *Circle*- the rotation of Earth; the spinning of a wheel; the blades of a helicopter; a yo-yo 3. *Arc*- the path of a home run hit; an arrow or rifle shot; a hypnotist's watch; a clock pendulum; a golf swing 4. *Vibration (back and forth)*- a guitar string; compressed spring that is released; snare drum head
What is the significance of defining a coordinate system to study the motion of an object?
A coordinate system tells about the location of the zero point of the variables defining the motion of the object to be studied. The coordinate system also explains the direction in which the values of the variables increase.
Explain the difference between average velocity and instantaneous velocity.
Average velocity provides the overall change in position of an object during a time interval. It does not describe any specific changes in the motion of the object over the course of the time interval. Instanteous velocity gives the speed and direction of an object at a particular instant during a time interval.
What is the difference between average velocity and average speed?
Average velocity shows both the magnitude and the direction of the motion of an object during a time interval. Average speed shows only how fast the object is moving (not the direction of motion).
What is the equation of motion for average velocity?
D = vt + di - d is the position of an object - v is the average velocity of the object - t is the time - di is the initial position of the object
How is displacement different from distance? Under what conditions can an object travel a certain distance and yet its resultant displacement be zero?
Displacement is a vector quantity, while distance is a scalar quantity. Displacement has both the magnitude and direction. Distance has only magnitude. The displacement of an object is equal to the difference between its final position and initial position. When an object starts moving from a certain point and after covering certain distance returns to its starting position, its displacement becomes zero.
Under what circumstances can the average velocity of a moving object be zero when its average speed is 50 km/hr?
If the object travels a distance, and then returns to its starting point, the average velocity will be zero because the overall displacement will be zero.
For constant time intervals in a motion diagram, what can be concluded about a moving object that has smaller and smaller distances between images of the object?
The object is accelerating (slowing down).
For constant time intervals in a motion diagram, what can be concluded about a moving object that has larger and larger distances between images of the object?
The object is accelerating (speeding up).
If a motion diagram shows unequal distances between images of a moving object during equal time intervals, what can be inferred about the moving object?
The object is not moving at a constant speed; it is accelerating.
What information is provided by the points on the line of a position-time graph of an object?
The points on the line of a position-time graph of an object represent the most likely positions of the moving object in the times between the recorded data.
The position-time graph of an object is found to be a straight line passing through the origin. What information about the motion of the object is provided by the graph?
The straight line position-time graph of a moving object gives the information about the nature of the motion of the object. It is also used to calculate the average velocity of the object. Since the graph is a straight line, the object is undergoing uniform motion. The slope of this line gives the value of the average velocity of the object.
How is the time interval affected when the origin of the coordinate system of a motion diagram is changed?
The time interval is a scalar quantity. Its value is not affected by the change in the relative position of the origin of the coordinate system.
Why is it important to choose a coordinate system of the same order of magnitude as the motion being described?
Using a coordinate system of a different order of magnitude than the motion being described could lead to loss of detail (if the coordinate system is too large for the motion being described). or the use of too many computing resources to describe the motion being studied (if the coordinate system is too small for the motion being described).
What is a motion diagram?
a series of images showing the positions of a moving object at equal time intervals
What are the two attributes of the coordinate system chosen for a motion diagram?
the origin and the axis of the coordinate system
What is the equation of motion for average speed?
|v|= | df-di/tf-ti |