Velocity

• The speed and direction of an object’s motion.

–88 km / hr southwest

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VELOCITYSPEED IN A GIVEN

DIRECTION

Vd

t=

direction

A bird flies south at 20 m/s.

• SPEED = 20 m/s

• VELOCITY = 20 m/s south

CONSTANT VELOCITY

CHANGING VELOCITY

COMBINING VELOCITIESCOMBINING VELOCITIES

How fast will this ball move?

What factors may affect its speed?

COMBINING VELOCITIES

Rowing speed = 16 km/hr

River speed (downstream)

= 10 km/hr

Combined velocity: 26 km/hr

V1(Boat) = 16 km/hr

V2 (river) = 10 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

D= 500m

D= 500m

T= 10 min

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 Ave S = total D/total T

2.Work 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 V= d/t with dir2. Work V= 500m/600s to friend’s house

3. Answer 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

Given: d= 800 m t= 180 s running at constant speed

1. Formula S= d/t 2. Work V= 800m/180s around oval3. Answer V= 4.44 m/s around oval

a.What is Sean’s speed in m/s?

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 CV= V1 + V22. Work CV= 16 km/h + 10 km/h

downstream 3. Answer 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 CV= V1 - V22. Work CV= 16 km/h - 10 km/h upstream

3. Answer CV= 6 km/h upstream