Chapter 11 review

Relative motion-

movement in relation to a frame of reference

Linear graph-

the displayed data form straight-line parts. The slope of the line is acceleration

Distance-

the length of a path between two points

Free fall-

the movement of an object toward earth solely because of gravity

Instantaneous speed-

the rate at which an object is moving at a given moment in time

Acceleration-

the rate at which velocity changes

Speed-

the ratio of the distance an object moves to the amount of time the object moves

Velocity-

the speed and direction in which an object is moving

Average speed-

the total distance traveled divided by the time it takes to travel that distance

Resultant vector-

the vector sum of two or more vectors

Why is choice of unit important when measuring distances?

The choice of unit is important when measuring distance because choosing the appropriate unit helps us not to make computing errors. If we choose the wrong unit, the quantity either results in an extremely small or large number. This is hard to estimate and would lead to errors when trying to work with the number. We want to use smaller numbers. Smaller numbers are easier to use.

Does a car's speedometer show instantaneous speed, average speed, or velocity? Explain.

A car's speedometer shows instantaneous speed because it gives the rate at which the car is moving at a given moment in time.

Why is a distance-time graph a good way to describe motion?

A distance-time graph is a good way to describe motion because the slope of the line on a distance-time graph indicates the speed of the object. It gives you a helpful visual to find what you're looking for.

Describe frame of reference and why it is necessary when considering motion? Give an example.

A frame of reference is a system of objects that are not moving with respect to one another. A frame of reference is necessary when considering motion because it describes motion completely and accurately. An example is a spaceship moving around the earth. It depends on your frame of reference on whether the earth moves or the spaceship moves. The most accurate frame of reference is when you're not moving.

How does a graph of constant acceleration differ from one showing constant speed?

A graph of constant acceleration is going up or down in a straight line but a graph of constant speed is a horizontal line.

A negative change in speed means an object is going _______________.

A negative change in speed means an object is going slower.

A positive change in speed means an object is going _______________.

A positive change in speed means an object is going faster.

What is a resultant vector? Is it a measurement of distance or displacement?

A resultant vector is the vector sum of two or more vectors. A resultant vector is a measure of displacement. Example: Forward 3 steps, backward 2 steps. Resultant vector = 1 step displacement.

Describe vector. How are vectors similar to displacement?

A vector is a quantity that has magnitude and direction. Vectors are similar to displacement because displacement is an example of a vector. Displacement has direction of the straight line and length of the straight line. {Magnitude and direction} Magnitude is quantitative and always has a #

How are the changes in velocity described?

Acceleration can be described as changes in speed, changes in direction, or changes in both. Acceleration is a vector.

Describe Acceleration.

Acceleration is a change in speed, direction, or both. It is the rate at which velocity changes.

How is acceleration an example of a vector?

Acceleration is an example of a vector because it has a magnitude which is speed and a direction.

How do you add displacements?

Add displacements using vector addition.

Two trains leave the station at the same time. Train A travels at a constants speed of 16 m/s. Train B starts at 8.0 m/s but accelerates constantly at 1.0 m/s2, After 10.0 seconds, which train has the greater speed?

After 10 seconds, Train B has a greater speed because with each second train B gets faster by 1 m/s, after ten seconds Train B would be at 18 m/s.

After completing circular motion why is the displacement 0?

After completing circular motion the displacement is 0 because the length of the straight line from the starting point to the stopping point is 0. You end up in the same place you started.

Describe an object experiencing constant acceleration.

An object experiencing constant acceleration is constantly changing in velocity at a consistent pace. Each second has the same change as the second before it.

What is the acceleration rate of an object moving at constant speed?

An object moving at constant speed has the acceleration rate of 0. ITS NOT CHANGING!

How are instantaneous speed and average speed different?

Average speed is computed for the entire duration of a trip, and instantaneous speed is measured at a particular instant.

Give examples of when average and instantaneous speed would be useful.

Average speed would be useful when you are driving around town to get to a certain location. You might travel slowly when the speed limit is lower and faster when the speed limit is higher. It is useful to know how fast you move, or your average speed, over the entire trip. Average speed would also let you know how long the trip will take. Instantaneous speed would be useful when you want to know the exact speed you are traveling in your car at a given moment. You can do this by looking at your car's speedometer.

Describe Free Fall.

Free fall is the movement of an object toward Earth solely because of gravity.

In Figure 4 on page 331 there is a red path and a yellow path. How can their displacements be the same when their distances are different?

The displacements of the red path and the yellow path can be the same when their distances are different because the displacement of both paths is a straight line that points directly from the starting point to the ending point. Because both paths start at the same place and end at the same place as each other, their displacements are equal.

What is the formula for calculating acceleration in straight-line motion?

The formula for calculating acceleration in straight-line motion is (v1 - v0) over t, which is change in velocity over time.

How can you find the speed from a distance-time graph?

The slope of a line on a distance-time graph is speed.

What does the slope of a line on a distance-time graph tell you?

The slope of a line on a distance-time graph tells you the average speed of an object.

How does a speed-time graph indicate acceleration?

The slope of a speed time graph is acceleration

What does the slope on a speed-time graph indicate?

The slope of a speed-time graph indicates acceleration.

Explain why the slope on a distance-time graph is speed.

The slope on a distance-time graph is speed because speed is the ratio of the distance an object moves to the amount of time the object moves. In order to find the slope of a distance time graph, you have to divide the distance an object travels by the amount of time it takes.

What symbol is used for average speed? How is average speed calculated?

The symbol used for average speed is v̅. Average speed is the total distance traveled divided by the time is takes to travel that distance.

What symbol is used for instantaneous speed? Give an example of how instantaneous speed can be calculated.

The symbol used for instantaneous speed is v. An example of how instantaneous speed can be calculated would be the following: The speedometer in a car measures the car's instantaneous speed. If the car was moving 50 miles per hour, you could describe the car as moving 50m/h. You need to be doing the action to record instantaneous speed. A device is needed for observation.

List the two noted ways to express speed. How are they different?

The two noted ways to express speed are average speed and instantaneous speed. Average speed is computed for the entire duration of the trip, while instantaneous speed is measured at a particular instant.

What is the unit for acceleration?

The unit for acceleration is meters per second squared m/s2.

The resultant vector of two particular displacement vectors does not equal the sum of the magnitude of the individual vectors. Describe the directions of the two vectors.

The vectors are right angles to each other.

Would you measure the height of a building in meters? Give reason for your answer.

You would measure the height of a building in meters. The length of multiple meters conveniently fits the scale of a building. A building measured in meters give and answer that's not too large or too small. Meters give a reasonable precision.

Should your directions to a friend for traveling from one city to another include displacements or distances?

Your directions should include distances. Distances describe how far your friend has to go and in what direction they must travel to get there. Displacement would work if you flew over the city in a straight line.

Nonlinear graph-

a curve connects the data points that are plotted

Vector-

a quantity that has magnitude and direction

Constant acceleration-

a steady change in velocity

Frame of reference-

a system of objects that are not moving with respect to one another

In the Daytona 500, why do the cars constantly fight for inside position?

Cars constantly fight for inside position because the inside of the track is smaller than the outside so you have less ground to cover.

How does a change in direction affect acceleration?

Change in direction is part of acceleration. If you are changing direction you are accelerating.

How are deceleration and acceleration related?

Deceleration is just a form of acceleration. Acceleration describes the the change in speed or direction, but deceleration is the slowing down of an object.

Why is direction important when adding vectors?

Direction is important when adding vectors because when two displacements, represented by two vectors, have the same direction, you can add their magnitudes. If the vectors are in opposite directions, you subtract their magnitude. You are trying to consider the position.

Is displacement more like the length of a rope that is pulled tight or the length of a coiled rope?

Displacement is more like the length of a rope that is pulled tight because a coiled rope does not have a direction.

Describe displacement. How is displacement important when considering distance?

Displacement is the direction from the starting point and the length of a straight line from the starting point to the ending point. Displacement is important when considering distance because it describes how far away and in what direction the object is from a given point.

How is distance determined? In what context are standard distances considered?

Distance is determined by measuring the length of the line connecting the object's starting point and its ending point. Distance is the length of a path between two points. Distance is considered in the context of variable units according to the magnitude of the distance. The two points have a definite position. They have to be specific.

How are distance and displacement different?

Distance is the length of the path between two points. Displacement is the direction from the starting point and the length of a straight line from the starting point to the ending point.

What is instantaneous acceleration?

How fast a velocity is changing at a specific instant

How does this formula indicate positive and negative acceleration?

If acceleration increases, the numerator would be positive and therefore the acceleration would be positive. However, if acceleration decreases the numerator would be negative and therefore the acceleration would be negative.

If the slope of line "A" on a distance time graph is steeper than line "B", what can you infer?

If the slope of line "A" on a distance-time graph is steeper than line "B", you can infer that the the object representing line "A" has a faster speed than the object representing line "B". A steeper slope on a distance-time graph indicates a higher speed.

If there are multiple frames of reference to choose from, how do you decide which to use?

If there are multiple frames of reference to choose from, you decide which to use by determining which frame is the most convenient or the frame of reference which gives the best framework for the solution to your problem.

Describe instantaneous acceleration.

Instantaneous acceleration is how fast velocity is changing at a specific moment.

Differentiate between the common use of the term acceleration with how a scientist would use it.

Most people use the term acceleration as a change in speed, usually when speed is increasing. Acceleration is actually a change in speed or direction, whether the speed is increasing or decreasing.

Describe relative motion. How can relative motion vary? Example?

Relative motion is movement in relation to a frame of reference. Relative motion can vary because it depends on the frame of reference you choose to measure the the object's motion. An example is if you are in a car on the highway. If you stand on the side of the road and watch the car go by, the car will appear to move fast. However, if you are sitting in the car and look around, the people sitting next to you will not appear to be moving.

Define speed. What is the SI unit for speed?

Speed is the ratio of the distance an object moves to the amount of time an object moves. Speed is how fast you are going. The SI unit of speed is meters per second (m/s).

Suppose you plot the distance traveled by an object at various times and you discover that the graph is not in a straight line. What does this indicate about the object's acceleration?

This indicates that the object is not constantly accelerating. It is still accelerating, but not in a constant way

What is needed to describe motion completely?

To describe motion accurately and completely, a frame of reference is necessary.

How do velocities add?

Two or more velocities add by vector addition.

How are speed and velocity different?

Velocity is a description of both speed and direction of motion. Velocity is a vector.

Describe velocity. How is velocity an example of a vector?

Velocity is a description of both speed and direction of motion. Velocity is an example of a vector because it has both magnitude and direction.

How do we describe the motion of an object? What 3 things do we need to know?

We describe the motion of an object using a frame of reference. The 3 things we need to know are the direction the object is moving, how fast the object is moving, and its location at a certain time.

How can you calculate acceleration?

You calculate acceleration for straight-line motion by dividing the change in velocity by the total time

How do you calculate the magnitude of the resultant velocity of two vectors a right angles to each other?

You calculate the magnitude of the resultant velocity of two vectors at right angles to each other by squaring both of the vectors and adding them together, using Pythagorean Theorem. A2 + B2 = C2

Describe an Experiment you could perform to determine the average speed of a toy car rolling down an incline.

You could determine the average speed of a toy car rolling down an incline by first measuring the distance the car travels and the time it takes the car to travel down the incline. You could then graph the distance/time of the car on a distance-time graph and find the slope of the line. The slope would equal the average speed of the toy car.