Frame of Reference Whenever you describe something moving you are comparing it to something that is not moving. The thing that is not moving is the frame of reference. It is usually the background.

Relationship between motion and frame of reference Motion is any change in position over a certain amount of time. Frame of reference depends on: Type of movement The position from which you are observing.

What is the frame of reference? The sun is rising over the mountains. The earth

Calculate average speed of an object. Speed is the rate at which an object moves. Formula: S = Distance / Time, s = D/T Measured in meter/sec, m/s or km/hr Average speed is the total distance divided by the total time. Constant speed is the speed of an object at every point in it journey.

Graphing speed Average speed Velocity Total distance / total time Meters / sec Velocity Speed in a given direction. Velocity = distance / time miles/hr west The x axis is always labeled as time The y axis is always labeled at distance.

Combining velocities To combine velocities you add them together. If a river is moving at 5 m/s and you are rowing at 12 m/s, what is your total velocity? 17 m/s What if the wind is blowing 50 mph and the plane is flying into the wind at 250 mph. What is the velocity of the plane? 250 mph - 50 mph 200 mph

Acceleration The rate of change in velocity. Formula Accel. = Final Velocity - Original Velocity Time A roller coaster at the top of a hill has a velocity of 10 m/s. Two seconds later it reaches the bottom of the hill with a velocity of 26 m/s. What is the acceleration of the roller coaster? 26m/s - 10 m/s 2 sec 8 m/s/s or 8 m/s2

Practice Problems A roller coaster is moving at 25 m/s at the bottom of a hill. 3 seconds later it reaches the top of the hill moving at 10 m/s. What is the deceleration of the roller coaster? 5 m/s A car is traveling at 60 km/hr. It accelerates to 85 km/hr in 5 seconds. What is the acceleration of the car? 5km/hr/sec

Momentum Momentum depends on the mass of an object and the velocity it is traveling. If either mass or velocity is large then the object has a large momentum. Momentum = mass x Velocity g m/s What is the momentum of a .30kg bluejay flying at 17 m/s? 5.1 kg*m/s

Conservation of Momentum The total momentum of any group of objects remains the same unless outside forces act on those objects. Practice What is the momentum if a skier has a mass of 60 kg and a velocity of 20m/s? 1200kg*m/s What is the momentum of an object that has a mass of 2 kg and a velocity of 4 m/s? 8 kg m/s