Chapter 4 Motion 4 1 Speed and Velocity

Chapter 4: Motion 4. 1 Speed and Velocity https: //www. youtube. com/watch? v=DRb 5 PSx. Jer. M

Algebra Review Solve for x 10 = 5 x 10 = x 5

Algebra Review Solve for 10 = 3

Speed • speed: how quickly something moves

Types of Speed • average speed: the total distance of a trip divided by the total time • instantaneous speed: the actual speed an object has at a given moment

Velocity • velocity: speed with direction • Use the same equation! • Positive when moving forward • Negative when moving backward

Example 1 • An object has travelled 100 km in 5 hours. What is its speed? 1. Looking for: speed (km/hr) 2. Given: distance (100 km), time (5 hours) 3. Relationships (equations): v = d/t 4. Solution: v=d/t, v = 100 km/5 hrs = 20 km/hr

Example 2 • A plane made it from Los Angeles, CA to Sydney, Australia (a distance of 12, 065 km) in 22 hours. What speed was it travelling at? 1. Looking for: speed 2. Given: distance (12, 065 km), time (22 hours) 3. Relationships (equations): v = d/t 4. Solution: v = 12, 065 km/22 hr = 550 km/hr

Example 3 • A car is going 40 km/hr, how far has it gone (or “distance”) after 3 hours? 40 km 1 hr 1 hr 1. Looking for: distance (km) 2. Given: speed (40 km/hr), time (3 hrs) 3. Relationships (equations): v = d/t 4. Solution: d= 40 km/hr * 3 hr … 120 km 5. or ~100 km (sig digs)

Example 4 A train travels at 100 km/hr heading east to reach a town in 4 hours. The train then reverses and heads west at 50 km/hr for 4 hours. What is the train’s position now compared to where it started? 1. Looking for: Distance/(Position) 2. Given: speed and time both ways 3. Relationships (equations): v = d/t 4. Solution: to the right = 400 km, to the left = 200 km

Example 5 • A boat is moving at 20 m/sec. How long will it take the boat to get somewhere 390 m away? 1. Looking for: time (sec) 2. Given: speed (20 m/sec), distance (390 m) 3. Relationships (equations): v = d/t 4. Solution: v=d/t, 20=390/t, 20 t=390, = 19. 5 sec

Example Problem 6 • A jet ski makes it across a lake in 30 seconds. If the lake is 100 km long, how fast is the jet ski going? • Looking for? Speed • What we know? Distance/time (100 km/30 sec) • Relationship? V=d/t • Solution? V=100 km/30 sec = 3 km/sec

Example Problem 7 • A rescue helicopter is moving at 8 m/s. If it makes it to its destination in 120 seconds, how many meters did it travel? • • Looking for? Distance Known? Velocity, Time (8 m/s and 120 sec) Relationship? V=d/t Solution? 960 meters

Example Problem 8 • A rocket launches into space, going through 480 km of the atmosphere in 2 minutes. How fast is the rocket going? • • Looking for? Speed Known? Distance (480 km) and Time (2 min) Relationship? v = d/t Solution? 240 km/min = 14, 400 km/s