Chapter 1 Force and motion

Bell Work Draw pictures to represent the motion described in these two scenarios. An ant crawls across the top of your shoe, from left to right. A hiker walks from the beginning to the end of a hiking path.

1/25/12 - How do you describe the location of an object? Choose an object in the classroom that is easy to see Without pointing to, describing, or naming the object, write down directions for your partner to find the object. Trade papers with your partner and see if they can find your object. If your partner cannot find the object do not tell them what it is instead rewrite the directions and have your partner try again.

Answer these questions on the back of your piece of paper. Was your partner able to find your object on the first try? Second try? What difficulties did you have in writing down the directions? What difficulties did you have in trying to follow your partner’s directions? What kind of information must you give another person when you are trying to describe a location?

Force and Motion 1.1 Notes

position the location of a place or object Each time you identify the position of an object, you are comparing the location of the object with the location of another object or place. Why do you need to use two locations to describe the position of an object?

Describing a position What are two ways that you could describe the location of a city? Reference point – a location to which you compare other locations Longitude and latitude system – locations are given by two numbers longitude (how many degrees east or west it is from the prime meridian) and latitude (how many degrees north or south it is from the equator)

Measuring distance What unit do scientists use to measure distance? A meter There are two ways to measure distance Straight line distance Total length of a path taken between two positions

How do you know that motion has occurred? There is a distance between starting and ending positions of an object. Motion – the change of position over time Below, while jumping, the athlete’s horizontal and vertical positions change.

Describing motion The speed of a moving object is a measure of how quickly or slowly the object changes a position. Compare the motion of a fast moving object to a slow moving object in a given amount of time. The way in which an object moves can change. Discuss the movement of a raft in the water.

Relative Motion How an observer sees your motion depends on how it compares with his own motion. Frame of reference – motion is described by the location of the observer See page 13 relative motion on a school bus

Bell Work What information do you need to describe an object’s location? Describe how your position changes as you jump over an object. Kyle walks 3 blocks south from his home to school, and Jana walks 2 blocks north from her home to Kyle’s home. How far and in what direction is the school from Jana’s home?

Bell Work Please use complete sentences If you sit in a moving bus and toss a coin straight up into the air, where will it land? What is a reference point? What is a position? What is motion?

Motion 1.2 Notes Speed – a measure of how fast something moves or the distance it moves, in a given amount of time Rate – the way in which one quantity changes compared to another quantity Speed is the rate at which the distance an object moves changes compared to time

Calculating Speed To calculate speed you need to know 2 measurements Distance Time Speed = distance S = d time t Standard unit is meters/second (m/s) Also given in kilometers/hour (km/hr) US – miles/hour (mi/h or mph) 1mph = 0.45m/s

Practice Calculating Speed A wheelchair racer completes a 100-meter course in 20 seconds. What is his speed? Speed = 5 meters/second A man runs 200 meters in 25 seconds. What is his speed? S = 8 m/s If you travel 100 m in 50 s, what is your speed? S = 2 m/s

Bell Work DO NOT TOUCH THE COMPUTERS!! Be sure to show all of your work!! 1. What is the definition for speed in your own words? 2. What is the speed of an object that travels 15 meters in 3 seconds. 3. What is the speed of an object that travels 120 miles in 2 hours.

Average speed Speed is not constant. For example, when you run, you might slow down to pace yourself, or speed up to win a race. At each point you are running, you have a specific speed. Instantaneous speed – moment-to-moment speed Average speed over a distance is a lot easier to calculate than instantaneous speed

Distance-Time Graph Used to show the motion of an object by using a graph that plots the distance the object has traveled against time See page 20-21

Bell Work Round to the nearest hundredth and show all of your work!! What is the average speed of a person that runs 22 miles in 3 hours? What is the average speed of a lion if it goes 750 meters in the first 100 seconds then rests for 20 seconds then runs 1250 meters in 80 seconds? A plane travels from St. Louis to Florida in 2.5 hours. The distance from St. Louis to Florida is about 700 miles. What is the planes average speed?

Velocity – a speed in a specific direction 2 people moving at the same speed but opposite directions have different velocities 2 people moving in the same direction but at different speeds have different velocities 2 people moving in the same direction and at the same speed have the same velocities

Vector – a quantity that has both size and direction Is speed a vector? No, because speed is a measure of how fast or slow an object moves, not which direction it moves in. Is velocity a vector? Yes, because velocity has a size – the speed – and a direction, so it has a vector quantity.

Practice drawing vectors Draw vectors representing the movement of the following ant. The ant moves right at 1 m/s The ant moves upward at 2 m/s The ant moves right at 0.5 m/s The ant moves downward at 1 m/s

Average velocity – depends on the total distance you have traveled Suppose you are playing catch with a friend. You throw the ball to your friend at 2 m/s in a north direction. Your friend throws the ball back to you at 2 m/s in a south direction. Draw vectors to represent this. What is the average speed of the ball? What is the average velocity of the ball?

Velocity vs. Speed Make a Venn diagram comparing and contrasting speed and velocity.

Bell Work Write each of these statements on your bell work sheet then decide if they are true or false. If false, change them so they are true. A distance-time graph shows how speed changes with time. Speed is a vector. Average speed is total distance multiplied by total time.

Motion 1.3 Notes Acceleration – a measure of how quickly the velocity is changing. Acceleration = final velocity – initial velocity time

Practice calculating acceleration Ama starts sliding with a velocity of 1 m/s. After 3 s, her velocity is 7 m/s. What is Ama’s acceleration?

More practice A man walking at 10 m/s accelerates to a velocity of 12 m/s in 2 s. What is his acceleration? A train traveling at 10 m/s slows down to a complete stop in 20 s. What is the acceleration of the train?

More practice A car starts a race and after 20 s is traveling at a velocity of 100 m/s. What is the acceleration of the car?

Bell work – show all work! If you traveled 200 m in 50 seconds, then 100 m in 30 seconds, then stopped for 5 seconds, and finished by sprinting 80 m in 5 seconds, what is your average speed? A sprinter starts a race at 5 m/s then 10 seconds later he finishes the race at 10 m/s. What is the acceleration of the runner?

Bell Work Please show your work. A cheetah runs 90 meters in 3 seconds. What is the cheetah’s speed? How long would it take an object traveling 12 m/s to go 60 m? A car traveling at 15 m/s slows down to a complete stop in 30 s. What is the acceleration of the car?

Bell Work Pg 35 #8-15 Please write only the number and the answers on your bell work paper we will be grading this

Bell Work What is speed? (write the definition and formula) What is velocity? What is acceleration? (write the definition and formula)