Kinematics
Day 3
Kinematic Equations
•
Used in
situations
with uniform
acceleration
2 2
2
/
2
1
2
f i
f i
i
V d t
V V at
V V ad
d Vt at
Kinematic Equations

Ex #1
•
A car traveling with an initial velocity
of 6 m/s, accelerates at 2 m/s
2
, for 6
seconds. What is the car’s final
velocity?
Kinematic Equations

Ex #1

Ans
•
A car traveling with an initial velocity of 6
m/s, accelerates at 2 m/s
2
, for 6 seconds.
What is the car’s final velocity?
2
6 2 6 18
f i
f
V V at
m m m
V s
s s s
Sample Problems
2. You’re riding a unicorn at 25 m/s
and come to a uniform stop at a
red light 20 m away. What’s your
acceleration?
A:

15.6m/s
2
Practice Problems
3. With an average acceleration of

1.2
m/s
2
, how long will it take a cyclist to
bring a bicycle with an initial speed of
6.5 m/s to a complete stop?
A: 5.4 s
Practice Problems
4. Suppose a treadmill has an average
acceleration of 4.7
×
10
3
m/s
2
.
a.
How much does its speed change
after 5.0 min?
b.
If the treadmill’s initial speed is 1.7
m/s, what will its final speed be?
1.4
×
10
6
m/s and
3.1 m/s
Practice Problems
4. A dune buggy accelerates uniformly at
1.5 m/s
2
from rest to 22 m/s. Then
the brakes are applied and it stops
2.5 s later. Find the total distance
traveled.
A: 188.8m
•
If a baseball has zero velocity at some instant, is
the acceleration of the baseball necessarily zero
at that instant?
•
If a passenger train is traveling on a straight track
with a negative velocity and a positive
acceleration, is it speeding up or slowing down?
•
When you are out for a bike ride, you slow down
on your bike as you approach a group of hikers
on a trail. Explain how your acceleration can be
positive even though your speed is decreasing.
Small Group Questions
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