11.2 speed and velocity slow versus fast movement can be described in terms of ___________ the speed...
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11.2 Speed and Velocity
Slow versus fast movement can be described in terms of ___________
The speed of an in-line skater is usually described in ________
The speed of a car is usually described in ___________.
speed
m/s
km/h
11.2 Speed and Velocity
Key Concepts
• How are instantaneous speed and average speed different?
• How can you find the speed from a distance-time graph?
• How are speed and velocity different?
• How do velocities add?
11.2 Speed and Velocity
Speed
Speed is the ratio of the _____________ an object moves to the amount of _____________ the object moves.
SI unit = meters per second ________.
Average speed is computed for the _________ duration of a trip
Instantaneous speed is measured at a particular _____________.
distance
time
m/s
entire
instant
11.2 Speed and Velocity
Calculating Average Speed _______
While traveling on vacation, you measure the times and distances traveled. You travel 35 kilometers in 0.4 hour.
v
35 km
.4 h= 87.5 km/h
11.2 Speed and Velocity
2. A train travels 190 kilometers in 3.0 hours, and then 120 kilometers in 2.0 hours. What is its average speed?
Total distance =
Total time =
Speed
190 km + 120 km = 310 km
3.0 h + 2.0 h310 km
= 5 h
5 h= 62 km/h
11.2 Speed and Velocity
Instantaneous Speed ____
Sometimes you need to know how fast you are going at a particular moment.
The speedometer in a car measures the car’s instantaneous speed
Notice the scale marking are given both in_______ and _______
v
km/h mph
11.2 Speed and Velocity
Graphing Motion
The ________ of a line on a distance-time graph is speed.
Use a point on the graph
to determine speed…
_d_
t
slope
= ______100 m
4 s
25 m/s
11.2 Speed and Velocity
A steeper slope on a distance-time graph indicates a _____________ speed.faster
11.2 Speed and Velocity
Velocity
Velocity is a description of both _____________ and ____________ of motion.
Velocity is a ____________.
To describe the velocity of a cheetah correctly, you must assess it’s speed and many directionalchanges
speed
direction
vector
11.2 Speed and Velocity
As the sailboat’s direction changes, its velocity also ______________, even if its speed stays the same.
Since velocity is a vector,
It can be represented __________
Velocity
changes
arrows
11.2 Speed and Velocity
Combining Velocities
Two or more velocities add by ___________ ________________.
Ex: If a boat is moving on a flowing
river, you must calculate the velocity
of the ______________ relative to the
riverbank and the velocity of the
______________ relative to the river.
Combined, they yield the velocity of the boat relative to the riverbank. 5 km/h + 12 km/h =
vector
addition
river
boat
17 km/h
11.2 Speed and Velocity
The resultant velocity shown is a combination of the current _______ and the velocity of the ____________ relative to the river
The _______________
resultant velocity is…
Combining Velocities
(x)
boat (y)
measured (z)
13 km/h
11.2 Speed and Velocity
You can also calculate the resultant velocity with the Pythagorean theorem formula…
x2 + y2 = z2
52 + 122 = z2
25 + 144 = z2
169 = z2
Combining Velocities
13 = z
11.2 Speed and Velocity
Assessment Questions
1. A woman jogs 10 kilometers in one hour, stops at a restaurant for one hour, and then walks 10 kilometers in two hours. What is her average speed for the outing? a. 0.2 km/h
b. 4 km/h _10 km + 10 km_
c. 5 km/h 1h + 1h + 2h
d. 10 km/h
11.2 Speed and Velocity
Assessment Questions
2. Lisa plotted time on the x-axis of a line graph and distance on the y-axis. What does the slope of her graph represent?a. total distance traveledb. velocityc. speedd. displacement
11.2 Speed and Velocity
Assessment Questions
3. A kayak is moving across a stream that is flowing downstream at a velocity of 4 km/h. The kayak’s velocity is 3 km/h. What is the magnitude of the kayak’s velocity relative to the river bank? a. 1.3 km/h
b. 5 km/h
c. 7 km/h
d. 12 km/h
4 km/h
3 km/h32 + 42 = z2
9 + 16 = z2
25 = z2
11.2 Speed and Velocity
Assessment Questions
4. The SI unit for speed of an airplane is miles per hour.
TrueFalse