Describing Motion

Identify 3 ways in which an object can accelerate.

Speed up
Slow down
Change direction

When describing position, which 2 factors change if the reference point changes?

Distance
Direction

What is motion?

The process of changing position

What is speed?

The distance an object travels per unit of time.

What is acceleration?

The measure of the change in velocity during a period of time.

What is displacement?

The difference between initial position and final position of an object. The "straight line" measurement from the starting point to the ending point.

What is distance?

The measure of the path that an object follows from its starting point to its ending point. If you take a trip, you measure the distance that you travelled rather than the displacement.

What is position?

an object's distance and direction from a reference point

What is a reference point?

the starting point that you choose to describe the location (or position) of an object

How do you calculate average speed?

distance divided by time

What is constant speed?

rate of change of position in which the same distance is traveled each second.

What is instantaneous speed?

speed at a specific moment (instant) in time. This is the speed that is shown by a spedometer or by a cop's radar gun.

What is velocity?

the speed and direction of an object moving

What happens when a reference point is changed?

The description of the distance and direction to the object also must be changed.

How can you tell whether or not an object is in motion?

Compare its position to that of a reference point. If the distance or direction to the reference point changes, it is in motion. If not, it isn't.

What is changing speed?

The amount of distance covered with each unit of time changes.

How can velocity change? (3 ways)

Change in speed
Change in direction
Change in both speed and direction

When your speed is increasing, are you accelerating in the direction the car is moving or in the opposite direction?

In the direction the car is moving

When your speed is decreasing, are you accelerating in the direction the car is moving or in the opposite direction?

In the opposite direction

What is the formula for acceleration?

acceleration=(final velocity-initial velocity)/time
See page 8 of your notes for this. I will provide the formula, but it will be written out as we wrote it on page 8.

What does each variable in the acceleration equation represent?

a=acceleration
Vf=final speed
Vi=initial speed
T=time

How is a stopped object (or an object at rest) indicated on a distance-time graph?

The graph will have distance on the y-axis and time on the x-axis. The students will draw a straight line with no slope beginning at the appropriate distance. If you are unsure about this, see page page 9 of your notes and refer to the top graph of set 1.

How is a stopped object (or an object at rest) indicated on a speed-time graph?

The graph will have speed on the y-axis and time on the x-axis. The students will draw a straight line with no slope beginning at a speed of 0. If you are unsure about this, see page page 9 of your notes and refer to the bottom graph of set 1.

How is constant speed represented on a distance-time graph?

The graph will have distance on the y-axis and time on the x-axis. The students will draw a straight line with the proper positive slope for that speed. If you are unsure about this, see page page 9 of your notes and refer to the top graph of set 2.

How is constant speed represented on a speed-time graph?

The graph will have speed on the y-axis and time on the x-axis. The students will draw a straight line with no slope from the appropriate speed. If you are unsure about this, see page page 9 of your notes and refer to the bottom graph of set 2.

How is acceleration represented on a distance-time graph?

The graph will have distance on the y-axis and time on the x-axis. The students will draw a curved line with positive slope. If you are unsure about this, see page page 9 of your notes and refer to the top graph of set 3.

How is acceleration represented on a speed-time graph?

The graph will have speed on the y-axis and time on the x-axis. The students will draw a straight line with positive slope. If you are unsure about this, see page page 9 of your notes and refer to the bottom graph of set 3.

What is the SI (standard) unit for speed?

meters/second (m/s)

What is the formula for speed?

v=d/t

In the speed formula, what does v stand for?

speed

In the speed formula, what does d stand for?

distance?

In the speed formula, what does t stand for?

time

If a car travels 400 m in 20 s, how fast is it going?

v=d/t
v=400 m/20 s
v=20 m/s

If you move 50 meters in 10 seconds, what is your speed?

v=d/t
v=50 m/10 s
v=5 m/s

How much time will it take for a bug to travel 5 meters across the floor if it is traveling at 1 m/s? t=d/v

t=d/v
t=5 m/1 m/s
t=5 s

In a competition, an athlete threw a discus 139 meters through the air. While in flight, the discus traveled at an average speed of 13.0 m/s. How long did the discus remain in the air? t=d/v

t=d/v
t=139 m/13.0 m/s
t=10.7 s

How far can a child run in 5 seconds if he travels at a rate of 2.5 m/s?

d=vt
d=(2.5 m/s)(5 s)
d=12.5 m

If a sprinter increases his speed from 3.0 m/s to 3.8 m/s over the course of 10 seconds, what is his acceleration?

a=(Vf-Vi)/t
a=(3.8 m/s-3.0 m/s)/10 s
a=0.08 m/s squared (I am unable to properly type the units in Quizlet)