Physics Chapter 3

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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


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