Velocity
• The speed and direction of an
object’s motion.
–88 km / hr southwest
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VELOCITY
SPEED IN A GIVEN
DIRECTION
d
V
=
t
direction
A bird flies south at
20 m/s.
• SPEED = 20 m/s
• VELOCITY = 20 m/s south
CONSTANT VELOCITY
CHANGING VELOCITY
COMBINING VELOCITIES
How fast will this ball move?
What factors may affect its
speed?
COMBINING VELOCITIES
Rowing speed
= 16 km/hr
River speed
V1(Boat) = 16 km/hr
V2 (river) = 10 km/hr
(downstream)
= 10 km/hr
Combined velocity: 26 km/hr
What is the velocity if you are
moving upstream?
Combined velocity:
(V1) 16 km/hr – (V2) 10 km/hr =
(CV) 6 km/hr
Why is the idea
of combining
velocities
important to
launching
rockets?
1. A runner moving eastward covers
a distance of a 100 meters in 10
seconds. What is his velocity?
Given: D= 100 m
T= 10s
dir= East
1.Formula
V= d/t with dir
2.Work
V= 100m/10s East
3.Answer
V= 10m/s East
2. A tropical disturbance spotted east of
the Philippines was moving at 60 km per
hour at a Northwesterly direction and
having maximum sustained winds of 150
km/h? What is the storm’s velocity?
Given: S= 60km/h
T= 10s
dir= NW
1.Formula
V= d/t with dir
2.Work/Answer
V= 60km/h NW
3. Seve is walking to a friend’s house. He walks 500m
for 10 minutes, then realizes he forgot something
important to bring. He turns around, and hurries back
to his house. The walk/jog back takes him 5 minutes.
Given: Total D= 500m + 500m = 1,000m
Total T= 10min + 5 min= 15min x 60 sec/min
= 900 sec
T= 10 min
D= 500m
D= 500m
T= 5 min
3. Seve is walking to a friend’s house. He walks 500m
for 10 minutes, then realizes he forgot something
important to bring. He turns around, and hurries back
to his house. The walk/jog back takes him 5 minutes.
a. What was his average speed in m/sec?
Given: Total D= 500m + 500m = 1,000m
Total T= 10min + 5 min= 15min x 60 sec/min
= 900 sec (15 min)
1.Formula
2.Work
Ave S = total D/total T
Ave S = 1,000m/900s
3.Answer Ave S = 1.1 m/s
3. Seve is walking to a friend’s house. He walks 500m
for 10 minutes, then realizes he forgot something
important to bring. He turns around, and hurries back
to his house. The walk/jog back takes him 5 minutes.
b. What was Seve’s velocity (in m/s) while walking to
his friend’s house?
Given: D= 500m T= 10min x 60 sec/min= 600 sec
dir = forward (to his friend’s house)
1.Formula
2. Work
3. Answer
V= d/t with dir
V= 500m/600s to friend’s house
V= 0.83 m/s to friend’s house
4. Sean is running around the track oval. The oval is
800m long. He is running at a constant speed. It
takes him 180 s to complete the track and get back
to where he started.
a. What is Sean’s speed in m/s?
Given: d= 800 m
t= 180 s
running at constant speed
a. What is Sean’s speed in m/s?
Given: d= 800 m
t= 180 s running at constant speed
1. Formula
2. Work
3. Answer
S= d/t
V= 800m/180s around oval
V= 4.44 m/s around oval
If Sean is running at constant speed, is he also
moving at constant velocity ?
No, he is always changing direction
(running around the oval).
3. A group of fishermen were rowing downstream at a
speed of 16 km/h.
a. How fast (combined velocity) is a group actually
moving if the river’s speed (downstream) is 10
km/hr?
Given: V1= 16km/h V2= 10 km/h dir= downstream
1.Formula
2. Work
3. Answer
CV= V1 + V2
CV= 16 km/h + 10 km/h downstream
CV= 26 km/h downstream
3. A group of fishermen were rowing downstream at a
speed of 16 km/h.
b. What will be their velocity if they
were moving upstream?
Given: V1= 16km/h V2= 10 km/h dir= downstream
1.Formula
2. Work
3. Answer
CV= V1 - V2
CV= 16 km/h - 10 km/h upstream
CV= 6 km/h upstream