# Velocity The speed and direction of an object’s motion. –88 km / hr southwest Image source:

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Velocity The speed and direction of an object’s motion. –88 km / hr southwest Image source: http://www.myteacherpages.com/http://www.myteacherpages.com/

VELOCITY SPEED IN A GIVEN DIRECTION V d 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 (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.FormulaV= d/t with dir 2.WorkV= 100m/10s East 3.AnswerV= 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/hT= 10s dir= NW 1.FormulaV= d/t with dir 2.Work/AnswerV= 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 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.FormulaAve S = total D/total T 2.Work Ave S = 1,000m/900s 3.AnswerAve 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.FormulaV= d/t with dir 2. WorkV= 500m/600s to friend’s house 3. AnswerV= 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

1. FormulaS= d/t 2. WorkV= 800m/180s around oval 3. AnswerV= 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.FormulaCV= V1 + V2 2. WorkCV= 16 km/h + 10 km/h downstream 3. AnswerCV= 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.FormulaCV= V1 - V2 2. WorkCV= 16 km/h - 10 km/h upstream 3. AnswerCV= 6 km/h upstream

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