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Mrs. W's Super Spectacular Science Site |
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Class Notes On this page you will find the daily class notes. They should be especially helpful to you if:1. You are absent and want to stay caught up on what happened in class,
2. You have gaps in your own notes, 3. You need another tool to help you study for a test. Matter in Motion Chapter 5 Section 1: Measuring Motion Observing Motion Reference Point – An object that appears to stay in place Motion – a change in position over time Reference Direction – EX: The cardinal and ordinal directions on a compass rose; left/right; up/down; backward/forward, etc. Common Reference Points 1. non-moving objects (mountains, buildings, trees) 2. moving objects (hot air balloon, birds) 3. Earth's surface (lakes, rivers, oceans, mountain ranges) 4. Earth (moves around the sun, relationship to other planets, stars) Speed Depends on Distance & Time Speed – the rate at which an object moves Depends On: 1. distance 2. time Calculating Average Speed: total distance/total time Problems to Practice 1. If you walk for 1.5 hours and travel 7.5 km, what is your average speed? _____km/h 2. A bird flies at a speed of 15 m/s for 10 s, 20 m/s for 10 s, and 25 m/s for 5 s. What is the bird’s average speed? _____m/s 3. What is your average speed if you take 0.5 hour to walk 4,000 m? _____m/h 4. If the average speed of a car is 110 km/h, how long will it take the car to travel 715 km? _____h Velocity: Direction Matters Velocity – the speed of an object in a particular direction Don’t confuse speed and velocity.
Velocity is the rate of change of an object’s position. Velocity is constant only if its speed and direction don’t change. Constant velocity is always along a straight line. Determining Resultant Velocity: the result of combining velocities RV (same direction): Add together to find resultant velocity RV (opposite direction): Acceleration – To accelerate means to change velocity. The faster the velocity changes, the greater the acceleration is Calculating Acceleration: Acceleration = Final velocity – Starting velocity/ time it takes to change velocity 1. A plane passes over Point A with a velocity of 8,000 m/s north. Forty seconds later it passes over Point B at a velocity of 10,000 m/s north. What is the plane’s acceleration from A to B? _____m/s/s north 2. A coconut falls from the top of a tree and reaches a velocity of 19.6 m/s when it hits the ground. It takes 2 s to reach the ground. What is the coconut’s acceleration? _____ m/s/s/ downward 3. In a summer storm, the wind is blowing with a velocity of 8 m/s north. Suddenly, in 3 seconds, the wind’s velocity is 23 m/s north. What is the acceleration in the wind? _____m/s/s/north |
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