Motion Notes Speed Velocity and Acceleration Motion l

Motion Notes Speed, Velocity, and Acceleration!

Motion l. A change in position, over time, relative to a reference point.

So, What’s a Reference Point? l http: //www. classzone. com/books/ml_scie nce_share/vis_sim/mfm 05_pg 7_relmotio n/mfm 05_pg 7_relmotion. html l What we compare all other movement or locations to! Often Earth Features l Large Objects l Cities l

Reference Point Scenarios Suppose you are in a train, and you cannot tell if you are stopped or moving. Outside the window, another train is slowly moving forward. What could be happening? Your train is stopped, and the other train is moving slowly forward… l The other train is stopped, and your train is moving slowly backwards… l Both trains are moving forward, with the other train moving a little faster… l Your train is moving very slowly backward, and the other train is moving slowly forward… l Could you be sure as to which is actually happening? ?

Reference Point Examples

Speed l Position can change at different rates l Distance an object moves in an amount of time l Formulas l Speed=Distance/Time l Distance=Speed x Time l Time= Distance/speed

Velocity Suppose there’s a TORNADO that’s 1 mile wide, and it’s going 40 mph… What else is important? !? !? It’s Direction! Velocity is a Speed in a Direction! 15 Mph Northwest; 200 m/s South; 40 cm/ms Left

Acceleration l l l Change in Velocity over time Remember: Velocity is Speed AND Direction “Speeding Up” = Acceleration (Positive #) “Slowing Down” = Deceleration (Negative #) Turning (Change in Direction) = Acceleration

Which of the Following Are Examples of Acceleration? l. A car stops at a stop light. l. A car goes from 0 to 45 mph. l. A car races around an oval track at a constant speed.

Acceleration Formula THIS IS TOUGH!!! Final Velocity – Initial Velocity Time Vfinal– Vinitial T

Acceleration Problem! Julio starts sliding with a velocity of 1 m/s south. After 3 seconds, his velocity is 7 m/s south. What is Julio’s acceleration? Final Velocity – Initial Velocity Time 7 m/s – 1 m/s 3 s 6 m/s 3 s 2 m/s 2

Practice! Review: Speed/Distance/Time Formulas: S=D÷T D=T·S T=D÷S Acceleration Formula: Final Velocity – Initial Velocity Time

Practice l. If a runner runs 100 meters in 50 seconds, what is his speed in meters per second? l. How far could this runner run in 25 seconds?

Calculating Acceleration l. John starts running from rest. After 10 s, his velocity is 20 m/s. What is John’s rate of acceleration?