Physics Chapter 3
Describe the motion of an object if its velocity-time graph is horizontal
The motion is constant
Acceleration -- scalar or vector?
Vector
Discuss the differences, if any, between the one-dimensional quantities (bold) d, |d|, and (italicized) d
(bold) d -- displacement |d| and (italicized) d -- magnitude of d, or distance
The absolute value of the slope of any time interval on a position-time graph gives the object's ____
Average speed in that time interval
What is the displacement divided by the time interval called?
Average velocity
The slope of a velocity-time curve represents A. Distance B. Velocity C. Displacement D. Acceleration
D. Acceleration
True or False: acceleration due to gravity is nearly constant at the earth's surface and is considered to be in the negative y-direction (pointing in the upward direction)
False. Acceleration due to gravity is nearly constant at the earth's surface and is considered to be in the negative y-direction (pointing in the downward direction)
True or False: Distance can be positive or negative.
False. Distance is always positive and it cannot give us information about the direction of movement
True or False: When working in 1 dimension at a time, represent scalar quantities with bold variables and subscript.
False. When working in 1 dimension at a time, represent vector quantities with italicized variables and subscript
Final velocity is directly proportional to the uniform acceleration calculated from an initial velocity V₂ = V₁ + a(triangle)t
First equation of motion
What is one common form of uniform acceleration?
Free fall
What is the area under a velocity-time graph, bounded by a specific time interval, numerically equal to?
Object's displacement
A graph of an object's position versus time
Position-time graph
If you graph the ordered pairs (t,x) for an object's position and time, what kind of graph is this?
Position-time graph
Change in time -- scalar or vector?
Scalar
What vector has a magnitude equal to the instantaneous speed?
The instantaneous velocity vector
The one-dimensional displacement or position of a system is proportional to the difference of the squares of its final and initial velocities during an interval and is inversely proportional to its uniform acceleration d = (v₂²-v₁²)/2a
Third equation of motion
Which equation of motion should you use if you do not know the elapsed time of an object's motion, assuming the necessary quantities are known?
Third equation of motion
What quantities must be known in order to find the displacement of an object using the second equation of motion?
Time interval, position, average acceleration, initial velocity, and initial position
True or False: Without a starting point (reference point, point of origin), we cannot prove that something has changed position
True
True or false: One dimension motion is represented on a number line
True
Under what condition(s) is the first equation of motion valid?
Valid for uniformly accelerated motion
A physical quantity that requires two pieces of information in order to be completely described -- a scalar value and a direction relative to a specified reference frame
Vector
Average velocity -- scalar or vector?
Vector
Change in position -- scalar or vector?
Vector
Change in velocity -- scalar or vector?
Vector
Displacement -- scalar or vector?
Vector
Does distance often differ from the object's displacement?
Yes, although in some cases (running in a straight line), distance and displacement can be equal
A ball is thrown straight up in the air and falls down to the ground. When the ball reaches its highest point (the instant before it changes direction and begins to fall), its velocity is
Zero
What is the formula for total/overall displacement?
d=x₃-x₁
In free fall, the acceleration is always
-9.81 m/s²
Which one of the following is a scalar quantity? A. Distance B. Velocity C. Displacement D. Acceleration
A. Distance
The time rate of change of velocity (v)
Acceleration
The slope of a position-time curve represents A. Distance B. Velocity C. Displacement D. Acceleration
B. Velocity
The resultant of a vector subtraction operation
Difference vector
The distance and direction between an object's position at one time and its position at a later time; in oscillatory motion, the distance and direction of the system from its equilibrium position
Displacement
What is the net change of position called?
Displacement
A student lives 5.0 km from his school. If he walks to school, turns around, and walks back home, what distance has he walked? What is his final displacement?
Distance: 10.0 km Displacement: 0.0 km
The branch of mechanics that mathematically describes the causes of motion
Dynamics
True or False: Displacement is positive only when the object has moved left (or down) from its initial position.
False. Displacement is positive only when the object has moved right (or up) from its initial position and it always give us both a number and directional information
The state of falling toward the earth or other planetary object under the influence of gravity only
Freefall
The speed of an object at a particular given time at that specific instant
Instantaneous speed
What does the study of kinematics describe?
It describes how objects move
The branch of mechanics that describe how systems move, without addressing what causes the motion
Kinematics
The absolute value of the measure of a quantity; the size of a measurement without regard to its direction or sign
Magnitude
The study of motion of macroscopic objects; the study of how (kinematics) and why (dynamics) things move
Mechanics
A quantity that can be completely described with only one piece of numerical information; a number that can be positive, negative, or zero
Scalar
Distance traveled -- scalar or vector?
Scalar
Instantaneous speed -- scalar or vector?
Scalar
Any quantity that includes a number (with or without units) only is a
Scalar Quantity
Displacement or position is dependent on the initial velocity, uniform acceleration, and the interval of time under consideration d = v₁(triangle)t + 1/2a(triangle)t² or x₂ = x₁ + v₁(triangle)t + 1/2a(triangle)t²
Second equation of motion
What are some factors that affect stopping distance?
Size of vehicle, initial speed, reaction time of the driver, road conditions (shape of road, surface material, and objects or substances on the surface)
What kind of kinematic information is provided by the slope of a velocity-time graph?
The acceleration of an object
How would you determine the average speed of a trip to Grandma's house?
The average speed is the ratio of the distance traveled |x₂-x₁| over an interval of time (t₂-t₁) v=|x₂-x₁|/(t₂-t₁)
How does increasing the number of data points on a position-time graph improve your ability to estimate instantaneous velocity at any point on the curve?
The smaller the interval, the better the estimate because you measure the instantaneous speed at a given point by calculating the average speed of a small interval containing that point
True or false: If speed is changing in an interval around that particular time, it isn't necessarily equal to the average speed on that interval and could be less than, greater than, or equal to the average speed for the interval
True
Linear motion in which acceleration during the time interval of interest is constant; motion in which the average acceleration equals the instantaneous acceleration
Uniformly accelerated motion
Motion in which the acceleration of an object is constant
Uniformly accelerated motion
Any quantity that includes both a magnitude (#) and a direction (can be a sin or a word) is called a
Vector Quantity
Are vector or scalar quantities usually represented by bold variables?
Vector quantities
The time rate of change in position in a specified direction
Velocity (v)
A graphical plot of velocity (usually one component) versus time; may be used to evaluate displacement and accelerations during selected time intervals
Velocity-time graph
The sign of the velocity (slope) tells us if the object is moving ____ or _____, up or down, etc.
forward or backward
What is the formula for distance?
s=|x₂-x₁|+|x₃-x₂|
A velocity-time graph has a ______ line.
straight
