Chapter 3

Question 1

Acceleration

Answer 1

The rate at which velocity is changing.
–> –>
Vavg = delta d / delta t
Units are m/s^2
Acceleration is a vector
Acceleration can be negative

Question 2

If an object is slowing down what is it called?

Answer 2

Deceleration, making the acceleration negative.

Question 3

Instantaneous velocity

Answer 3

The slope of the tangent to a point on a position-time graph.

Question 4

What happens when acceleration is constant?

Answer 4

The instantaneous velocity at the midpoint in time is equal to the average velocity for the whole trip.

Question 5

What can position time data be used for?

Answer 5

To produce a velocity-time graph for an object undergoing constant acceleration from rest.

Question 6

What does the slope of the velocity-time graph represent?

Answer 6

The acceleration of an object.

Question 7

What does it mean if the velocity-time graph of an object’s motion were not a straight line?

Answer 7

The accleration is not constant.

Question 8

What happens when acceleration is changing?

Answer 8

• average acceleration is found by calculating the slope of the line joining the endpoints of the time interval
  -instantaneous acceleration at a point in time is equal to the slope of the tangent at that point

Question 9

Does positive and negative acceleration mean the object is speeding up or slowing down?

Answer 9

No, it doesn’t necessarily mean the object is speeding up or slowing down if the acceleration is positive or negative.

Question 10

Differences Between Velocity and Acceleration:

Answer 10

1. Formula
2. Given position and time data, we can construct a graph to determine velocity.(slope) For accleration you need velocity and time data to construct a graph for acceleration.
3. Changing slope on a position-time graph means changing velocity (which is called acceleration)
   Whearas with acceleration, chaning slope on a velocity time-grraph means changing acceleration (called a jerk)

Question 11

PT 2: Differences Between Velocity and Acceleration:

Answer 11

4. Average velocity over a certain time period is determined by calculating the slope of the line joining the corrosponding points on a position time graph. But, average acceleration over a certain time period is determined by calculating the slope of the line joining the corresponding points on a velocity-time graph.
5. Velocity at a point is determined by calculating the slope of the tangfent line to the point on a position-time graph. With acceleration you calculate it the same but on a velocity-time graph.

Question 12

Constant Acceleration

Answer 12

The average velocity can also be found by averaging the initial and final velocities:
–> -> ->
Vavg = (V + V0) / 2

Question 13

What does the area under a –>v versus delta t graph represent?

Answer 13

The displacement during the time interval.
–> –>
delta d = V x delta t

Question 14

When do all objects fall to earth with the same constant acceleration?

Answer 14

In a vacuum and at the same location on the earth

Question 15

What does free fall mean?

Answer 15

There is no air resistance, the only thing affecting the object is gravity, and free fall is both on the way up and on the way down.

Question 16

Which way is the acceleration due to gravity?

Answer 16

Always downwards, whether the object is moving upward or downwards.

Question 17

What does g represent?

Answer 17

The magnitude of the acceleration due to gravity. the value of g is always a positive number. the actual value of g varies from place to place, it depends on how far you are from the center of the earth.

Question 18

What is the value of g on the top of a mountain compared to at sea levels, what is the value of g at the quarter or at the north and south poles?

Answer 18

It is lower on the top of a mountain and higher at sea levels. It is less at the equator than at both the north and south poles.

Question 19

The standard value of g:

Answer 19

9.80 m/s^2

Question 20

What do we usually treat up as when doing standard problems?

Answer 20

We usually treat up as the positive direction, and since gravity causes a downward acceleration, the acceleration is “-g”. However, as we’ll see soon, we sometimes define down as the positive direction, and so then the acceleration is “+g”.

Question 21

What do we replace an as in the formulas involving the magnitude of the acceleration due to gravity?

Answer 21

+g or -g instead of a

Question 22

When the motion is only downward, what will you choose to define the positive direction as?

Answer 22

The positive direction will be chosen as downwards.

Question 23

What does a position time graph that curves downwards represent?

Answer 23

A negative acceleration corresponds to a velocity graph whose slope is negative

Question 24

What does a position time graph that curves upwards represent?

Answer 24

A positive acceleration corresponds to a velocity graph whose slope is positive.

Question 25

when does direction change on a position time graph?

Answer 25

When the line changes direction

Question 26

when does direction change for a velocity-time graph?

Answer 26

if the line crosses over the x-axis from the negative to positive or positive to negative

Question 27

How to find displacement with a velocity-time graph?

Answer 27

In velocity versus time graphs, the displacements are given by the areas “under” (between the lines
and the time axis) the lines in the graphs.

Question 28

when an object is speeding up in the negative direction what is its acceleration?

Answer 28

negative

Question 29

when an object is slowing down in the negative direction what is its acceleration?

Answer 29

positive

Question 30

when an object is speeding up in the positive direction what is its acceleration?

Answer 30

positive

Question 31

when an object slows down in the positive direction, what is its acceleration?

Answer 31

negative

Question 32

what is changing acceleration called?

Answer 32

jerk