Presentation on theme: "Motion Chapter 11. Frame of Reference Motion must be described from a certain point of view – a frame of reference. Which way is up? Another example (begin."— Presentation transcript:
Frame of Reference Motion must be described from a certain point of view – a frame of reference. Which way is up? Another example (begin at 2:30) http://www.youtube.com/watch?v=ac6o8PXthzQ http://www.youtube.com/watch?v=i0g3g6AvLtM
Relative Motion Motion in a frame of reference is relative – that is it is compared to some other object. In physics the Earth is most often used as the frame of reference. What is the motion of the ball compared to the Earth in this clip? Compared to the truck?
Distance & Displacement Distance is how far you have traveled along a path. Displacement is how far you are from your starting point.
A vector is used to show each individual movement. The resultant vector is the sum of two or more vectors. In this case it shows the displacement.
Speed Speed is how far you have moved in a certain amount of time. Speed = distance/time Speed is a scalar. It has does not indicate direction. Average speed = total distance/total time Instantaneous speed is your speed at a certain moment (instant) of time.
Graphing speed The slope of a line on a distance-time graph is equal to the speed of the object. A straight line shows constant speed. A curved line shows acceleration.
Velocity Velocity is a vector. It is speed and direction. 70 mph = speed 70 mph east = velocity
Acceleration Acceleration is a change in velocity. – Change in speed, direction or both! It is a vector. A object in free fall is accelerating due to gravity alone. A g is about 9.8 m/s 2 (32 ft/s 2 ) Constant acceleration means that your velocity is changing steadily.
Graphs of Acceleration The slope of the line of a velocity-time graph is the acceleration of the object. If you calculate the area under a section of the graph you find the distance the object has traveled!