Acceleration Velocity Time Graphs Chapter 2 2 acceleration

Acceleration & Velocity Time Graphs Chapter 2. 2

acceleration • Rate at which velocity is changing acceleration= change of velocity time Acceleration = change of speed (along a straight line) time

• Acceleration occurs when there is either a change in speed, change in direction or both (whenever there is a change in velocity).

• In physics, acceleration applies to both increases and decreases in speed – Decrease in speed= negative acceleration

Practice Problem • Suppose a car moving in a straight line steadily increases its speed each second, first from 35 to 40 km/h, then from 40 to 45 km/h, then from 45 to 50 km/h. What is its acceleration? – Speed increases 5 km/h each 1 s interval, therefore acceleration= 5 km/h*s (read 5 km per hour second)

Practice Problem 2 • In 5 seconds a car moving in a straight line increases its speed from 50 km/h to 65 km/h, while a truck goes from rest to 15 km/h in a straight line in that same amount of time. Which undergoes the greater acceleration? What is the acceleration of each vehicle? – Acceleration for both vehicles is 15 km/h*s (the undergo the same acceleration even though their speeds are quite different)

Speed vs. Time Graphs • X axis: always time • Y axis: always speed • Slope of line = speed/time – Slope tells you what happens to acceleration of the object • Area under line tells you the distance the object traveled.

What is happening in this graph? • Objected started at rest • Speed is increasing • Object is accelerating

What is happening in this graph? • Object is slowing down • Object is negatively accelerating (decelerating)

What is happening in this graph? • Both objects are moving • Both objects are increasing speed but at different rates • Dashed line increases speed faster so it has the greater acceleration

What is happening in this graph?