P H Y S I C S  

Chapter 1: One-Dimensional Motion

Section 1B: Acceleration

Objectives:1)We will calculate the acceleration of an object

2)We will list the three ways an object can accelerate

Acceleration Equation

Change in velocity over time

a acceleration (m/s2) v final velocity (m/s) vo initial velocity (m/s) t time (s)

Acceleration

Three ways: Increase speed Decrease speed Change direction

Acceleration

Positive getting faster a = +10 m/s2

Negative getting slower a = -10 m/s2

Zero no change (constant) a = 0 m/s2

Usain Bolt (Olympic Sprinter)

Bolt vs. Gay vs. Powell Graph

Top Speed at 80 m Mark

Determine the acceleration for Usain Bolt over the first 80 m of the race if he reaches his top speed of 12.42 m/s (27.78 mi/h) at a time of 7.92 s.

a = 1.57 m/s2

Faster than a Car? (BMW 320d)

British Olympic Gold medalist Mark Lewis-Francis

Lewis-Francis vs. BMW 320d

∆x BMW 320d Lewis-Francis5 m 1.5 s 1.333

10 m 2.3 s 1.99020 m 3.3 s 3.13730 m 4.0 s 4.121

100 m 7.5 s 10.04 s

RESULTS

In-Class Problem #1

A shuttle bus slows down with an average acceleration of -1.8 m/s2. How long does it take the bus to slow from 9.0 m/s to a complete stop?

t = 5.0 s

In-Class Problem #2

In a game of Mario Kart, Luigi is lagging behind Mario. Luigi accelerates at a rate of 3.0 m/s2 for 1.5 s and reaches a speed of 14.0 m/s to pull past Mario. What was Luigi’s initial speed?

vo = 9.5 m/s

Assignment

Problem Set 1B 1A-1B Quiz (Displacement, Velocity &

Acceleration Quiz)