Acceleration
Ch. 10.2
ObjectivesDescribe the concept of acceleration as a change in
velocity.
Explain why circular motion is continuous acceleration even when the speed does not change.
Calculate acceleration as the rate at which velocity changes.
Graph acceleration on a velocity-time graph.
This Graph Shows Constant Velocity1. 2.
3.
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This Graph Shows No Velocity1.
2.
3.
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What is the distance a man can run in 1 hour if he runs at 7 mi/hr?
1. 7 km
2. 7 m
3. 7 mi
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What is the Velocity of a Plane that Travels 500 mi in 1 hour
1. 500m/s
2. 500 mi/hr
3. 500 km/hr
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Using the Conservation of Momentum if car has the momentum of 50 kg*m/s and a man is in the moving car the man
has?1. 50 m/s
2. 50 kg
3. 50 kg * m/s
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AccelerationAcceleration = change in velocity divided by
the time interval in which the change occurred.
Acceleration =
a =
final velocity – initial velocity
time
vf – vi
t
UnitsAcceleration = Vf – V i
t
Units = m or m
s2 s * s
AccelerationAcceleration = rate at which velocity changes
over time Quick time movie acceleration
Acceleration occurs when there's a change in SpeedDirectionOr both change
Uniform circular motion is constant acceleration.QT Centripetal AccelerationVideo of bucket and water having centripetal
acceleration
AccelerationAcceleration can be
determined from a graph
QT Graphical Representations of Accelerations
Acceleration can also be determined from a velocity-time graph
A straight line with slope = constant acceleration
Slope of the line = acceleration
Acceleration of a Bicycle
0
5
10
15
0 1 2 3 4
Time (s)
Ve
loc
ity
(m
/s)
Horizontal line = constant speed, no acceleration or deceleration.
Constant Velocity
0
10
20
0 1 2 3 4
Time (s)
Ve
loc
ity
(m
/s)
Examine the following graph.
0
5
10
15
20
0 2 4 6 8 10
Time (s)
Velo
city
(m/s
)
A negative slope indicates that an object is slowing down or decelerating.
Negative Acceleration (Deceleration) Graph
01020
0 1 2 3 4
Time (s)
Ve
loc
ity
(m
/s)
Calculating AccelerationAcceleration is the rate at which velocity changes.
Acceleration Equation (for straight-line motion) QT Distinguishing B/W Velocity and Acceleration QT Average Acceleration
SI Units = m/s2
acceleration = final velocity – initial velocity
time a = ∆vt
The Top Thrill Dragster at Cedar Point goes from 0 m/s to 53.6 m/s (120 mph) in 4 seconds. What is its acceleration?
Given:a =Vf
=
V i =
t =
Algebra:
Substitution:
A car traveling home at a velocity of 15.6 m/s slams on its brakes and comes
to a stop to avoid a dog. If it takes 5 seconds to stop, what is the cars
acceleration?Given:a =Vf
=
V i =
t =
Algebra:
Substitution:
In what direction is the car accelerating?
How can you tell mathematically?
A Porsche Boxster has an acceleration of 4.51 m/s2. If the car starts from rest how much time would it take for the vehicle to reach a speed of 11.3 m/s? Given:
a =Vf
=
V i =
t =
Algebra:
Substitution:
A golf ball thrown from the top of the sears tower accelerates at 9.8 m/s2 toward the ground and lands on the pavement 9.2 seconds. If the
ball’s final speed is 93.0 m/s what was the speed with which the ball was initial thrown?
Given:a =Vf
=
V i =
t =
Algebra:
Substitution: