Motion- A change in position relative to a fixed object Motion is one of the key topics in physics. Everything in the universe moves. It might only be a small amount and very slow, but movement does happen.

The physics of motion is all about forces. Forces need to act upon an object to get it moving. Motion won't just happen on its own. So how is all of this motion measured? Physicists use some basic terms when they look at motion.

Motion: A change in position relative to a fixed object Distance: The length between any 2 points in a path of objects

Speed - Speed is the term used to describe the distance traveled in a unit of time. The distance can be in a straight line or around a corner - all that speed describes is the rate of change of position.

Standard Units for Speed centimeters per second cm/s centimeters per minute cm/min foot/hour foot/second meters per second m/s miles/hour

A runner runs 400m in 100 sec.=4m/s »400/100= 4 Train goes 450km in 3 hours=150km/hr 450/3=150

5miles/.2hrs = 25 miles per hour

Velocity –Speed in a particular direction Velocity seems to be very similar to speed - it is quoted in meters per second or miles per hour and certainly describes the distance covered by a moving object in a unit of time - but with the extremely important addition that velocity is dependent on the direction of motion. Velocity has direction - and is known as a vector quantity. Velocity=distance and the Direction time

A plane flies 500 mph=Speed A plane flies 500mph southeast= Velocity

Look at the diagram showing the tracks of 4 jet fighters. All are travelling at the same speed knots Fighters A and C are travelling in the same direction so have the same velocities. Fighters B and D are travelling in different directions and have different velocities

Acceleration-Change of velocity per unit of time Change in speed or direction or both Acceleration can be negative or positive Final speed- original speed Time

Changing Your Velocity When velocity is changing, the word acceleration is used. A positive acceleration happens when you speed up. A negative acceleration happens when you slow down. When you accelerate or decelerate, you change your velocity over a specific amount of time. Final Velocity – Initial Velocity Time A swimmer increases their speed in the last 3 seconds of a race from 4m/s to 10m/s. 10-4= 2m/s 2 3

A baseball player decides to steal second base. He runs the distance (90ft) in 3 seconds Speed= 30ft/sec Acceleration= 30 ft/s – 0 ft/s = 3 s 10 ft/s/s

Graphing Distance(m) Time (s)

Slope and the Speed When you look at a slope of a line on a distance-time graph you may notice how slopes can be different. The slope of the line determines the speed; the higher the slope the greater the speed, but if the slope is low then the speed is low. Lets looks at the examples below As you can see in the first chart, the slope is very high, this means that the car must be traveling at a great speed. In the second graph, the slope is relatively low, which means that the car is driving at a very low speed