Physics 11
Chapter 4.1: Acceleration
Learning Intentions
I can:
 Define acceleration using words
 Define acceleration using a formula
 Use the definition of acceleration to solve problems involving velocity
and time
 Find the acceleration of an object given a velocity-time graph
 Draw velocity-time graphs for various scenarios
Definition
Consider the following displacement vs. time graph:
What is happening to the velocity between points AB, BC, CD, DE?
Physics 11
Although the average velocity is zero over the time period, the instantaneous
velocity has changed three times. The physical quantity causing this change in
velocity is known as ________________.
Definition:
Acceleration is defined as the rate at which the velocity of an object changes
over time and is expressed mathematically by the ratio of a change in velocity
(∆𝑣) to a time interval ((∆𝑡)
𝒂=
i.e.
∆𝒗
∆𝒕
=
𝒗𝟐 −𝒗𝟏
𝒕𝟐 −𝒕𝟏
Acceleration is measured in units of ____________________.
Example:
Determine the direction (+ or -) of the velocity and acceleration:
Scenario
Velocity
Acceleration
A car sitting at a stop light hits the gas
From rest you back out of your driveway
A plane lands and comes to a stop
You drop a rock off a cliff
You throw a rock straight up
Example:
A sprinter starts from rest and reaches a speed of 12
acceleration.
𝑚
𝑠
in 4.25 𝑠. Find his
Physics 11
On your Own:
𝑚
A car starts from rest and accelerates at 15 2 for 3.0 𝑠. What is its top speed?
𝑠
On your Own:
𝑚
𝑚
A snowboarder is traveling at 8.0 how long will it take her to reach 36.0 if
she can accelerate at a rate of 3.5
𝑠
𝑚
𝑠2
𝑠
?
Physics 11
Velocity vs. Time Graphs
Just like velocity with position-time graphs, the instantaneous acceleration of
an object is the slope of a velocity-time graph at that point in time.
On your Own
Consider the following velocity vs time graph:
Physics 11
a) What is the instantaneous acceleration at 𝑡 = 1𝑠 ?
b) What is the instantaneous acceleration at 𝑡 = 5 𝑠?
c) What is the instantaneous acceleration at 𝑡 = 11 𝑠?
Physics 11
d) What is the instantaneous acceleration at 𝑡 = 1𝑠 ?
Physics 11
Example:
Sketch 𝑣 vs. 𝑡 graphs of the following situations:
1) A hockey player skates at full speed then
comes to a sudden stop.
𝑚
2) A football is kicked straight up and then
falls back down.
𝑚
𝑣 (𝑠)
𝑣 (𝑠)
𝑡 (𝑠)
𝑡 (𝑠)
On your Own:
Sketch 𝑣 vs. 𝑡 graphs of the following situations:
3) A swimmer swims the length of a pool at a
constant speed, quickly turns around and
swims back.
4) A skydiver jumps from a plane, speeds up
to terminal velocity, falls for a while then
pulls the chute, slowing down.
𝑚
𝑣 (𝑠)
𝑚
𝑣 (𝑠)
𝑡 (𝑠)
**Assignment: CH 4.1 (p.64-70) 1, 2, 3, 4, 7**
𝑡 (𝑠)