Acceleration

COMPARING UNIFORM MOTION AND UNIFORMLY ACCELERATED a) Construct a Position vs. Time graph for an object moving right at 2.0cm/s Time(s) Position(cm) [→] 0.0 1.0 2.0 4.0 3.0 6.0 8.0

b) Construct a Velocity vs. Time graph for this same object Time(s) Velocity(cm/s) [→] 1.0 2.0 3.0 4.0

What is happening to the object in the following graphs? 𝑣

II) UNIFORM ACCELERATION →Occurs when an object travelling in a straight line changes its velocity uniformly with time 𝑣 𝑣 𝑡 𝑡

҉Example: Which of the velocities below involve uniform acceleration with an increasing velocity for the entire time? Describe the motion of the other sets Time(s) 0.0 1.0 2.0 3.0 Velocity (m/s) [E] 8.0 16.0 24.0 Velocity (m/s)[W] 4.0 Velocity (km/h)[N] 58 Velocity (m/s) [W] 15 16 17 18 Velocity (km/h)[S] 99 66 33

҉Example: Describe the motion illustrated in each velocity time graph shown below. Use terms such as uniform motion, uniform acceleration, and increasing or decreasing velocity In c) you can compare the magnitudes

Can you think of an example of an object experiencing non-uniform acceleration?

CALCULATING ACCELERATION Acceleration is the rate of change of velocity. Since velocity is a vector, so is acceleration In mathematical terms, acceleration is 𝒂 𝒂𝒗 = ∆𝒗 ∆𝒕 But, since ∆𝑣 = 𝑣 𝑓 − 𝑣 𝑖 then 𝒂 𝒂𝒗 = 𝑣 𝑓 − 𝑣 𝑖 ∆𝒕

This formula can be rearranged to 𝑣 𝑓 = 𝑣 𝑖 + 𝒂 𝒂𝒗 ∆𝒕 What are the units of acceleration? Calculating acceleration involves dividing velocity over time; therefore 𝒎/𝒔 𝒔 = 𝒎 𝒔×𝒔 = 𝒎 𝒔 𝟐 The SI unit for acceleration is meters per seconds squared.

҉Example: A car is moving at 108km/h [W], what acceleration would it have if it came to a complete stop in 5.0 seconds?

҉A distressed car is rolling backward, downhill at 3 ҉A distressed car is rolling backward, downhill at 3.0 m/s when its driver finally manages to get the engine started. What velocity will the car have 6.0 s later if it can accelerate at 3.0 m/s2?