Name: ___________________________
Block: ________
Unit 3 Acceleration
LESSON 3 -SUMMARY OF IMPORTANT KINEMATICS EQUATIONS
1. v
2.
f
 vi  at
d  v it  12 at 2
d  v a ve ra get
V average =
3.
v 2f  v 2i  2ad
• use
to find final velocity (vf) if given acceleration
(a), time (t), and initial velocity (vi)
• use
to find displacement covered if given initial
velocity (v), acceleration (a), and time (t)
• if the acceleration (a) is zero, the equation to find the
displacement (d) simplifies to this form. Use to find
displacement (d) given the average velocity
(vaverage) and time (t).
• use to find final velocity (vf) if given initial velocity
(vi), acceleration (a), and displacement
The formulas above work for the vector quantities, ________________and __________, as well as
for the scalar quantities, distance and speed. Remember to take the direction into consideration
when dealing with vector quantities; if you chose velocities to the right to be positive, then
velocities to the left would be __________________.
Sample Problems: Motion Equations (Part 1)
Solve the problems below, clearly showing all your work. Remember, you will use
these problems later to review this unit. Correct answers are shown to the right of each
problem.
v f  vi  at
1. Calculate the acceleration of a motorcyclist who accelerates from 6.0 m/s to 16.0 m/s in 5.0 s.
Solution:
Given Information:
v i  6.0 m s
t  5.0s
v f  16.0 m s
a ?
Substitution and Calculation:
v f  vi  at
(_______m s )  6.0 m s  a(_______s)
(_______m s )  a(_______s)
a  _______ m s 2
a = 2.0 m/s2
2. Jet airliners typically accelerate at a rate of 2.7 m/s2 for 35 s before they leave the ground. Calculate a jet airliner’s
take-off velocity.
Solution:
Given Information:
Substitution and Calculation:
v f  vi  at
v i  0.0 m s
t  (_______s)
a  (_______m s2 )
v f  (_______m s )  (_______m s2 )(_______s)
v f  _____ m s
vf  ?
3.
v = 94.5 m/s
When a jet airliner lands on a runway it accelerates at -1.9 m/s2 for 55 s until it stops. How fast was the plane
moving when it touched down on the runway?
Solution:
Given Information:
Substitution and Calculation:
v f  (_______m s )
t  55s
a  (_______m s2 )
v f  vi  at
(_______m s )  vi  (_______m s 2 )(_______s)
v i  _____ m s
vi  ?
v = 104.5 m/s
4. A motorcyclist is traveling at a velocity of 14.1 m/s when a car in front of the motorcycle skids to a stop. How
long would it take the motorcyclist to stop if the motorcycle can decelerate at a rate of -3.2 m/s2 ?
Solution:
Given Information:
Substitution and Calculation:
v i  (_______m s )
v f  (_______m s )
a  (_______m s2 )
t ?
v f  vi  at
(_______ s )  (_______m s )  (_______m s 2 )t
m
(_______m s )  (_______m s2 )t
t  _______ s
v = 4.4 s
Sample Problems: Motion Equations (Part 2)
Solve the problems below, clearly showing all your work. Remember, you will use
these problems later to review this unit. Correct answers are shown to the right of
each problem.
v f  vi  at
d  v it  12 at 2
v 2f  v 2i  2ad
1. A team of students competing in the ‘Egg Drop’ competition at the Physics Olympics at UBC, drop their egg from
a ledge, three floors above the ground.
a) If it takes the egg 2.4 seconds to reach the ground, calculate the height of the ledge in meters.
Solution:
Given Information:
v i  0.0 m s
t  (_______ s)
a  9.8 m s 2
Substitution and Calculation:
d  v it  12 at 2
d  _____m
d?
b) How fast was the egg traveling the instant before it hit the ground?
Solution:
2
d  (_______m s )(2.4 s)  12 (_______m s 2 )(_______s)
d = 28.2 m
Given Information:
Substitution and Calculation:
v i  (_______m s )
v f  vi  at
t  (_______s)
a  9.8 m s 2
v f  (_______m s )  (_______m s2 )(_______s)
v f  _______ m s
vf  ?
v = 23.5 m/s
c) The students had planned to protect the egg by dropping it into a garbage can filled with confetti, 0.85 m deep.
Assuming that the egg stopped just as it reached the bottom of the can, calculate the rate of deceleration of the
egg.
Solution:
Given Information:
Substitution and Calculation:
v i  23.5 m s
v f  (_______ m s )
(0.0 m s )2  (_______m s ) 2  2a(0.85m )
(_______m
d  (_______ m )
a ?
2
)  a(_______m )
a  _______ m s2
s2
a = -325 m/s2
1.
A book drops through two photogates. It passes the first gate at 6 m/s and the second at 30 m/s.
The acceleration due to gravity is 9.8 m/s2. How far is it between the photogates?
2.
A car accelerates at 4.0 m/s2 from 2.0 m/s to 26 m/s. How long did it take the car to reach 26
m/s?
3.
A block of wood is sliding along on level ice. Its original speed was 15 m/s. If it took 20.0
seconds to come to a complete stop, what was the acceleration due to friction?
Problem Set # 3: Motion Equations
Merill Pg. 72, 74, 77 & 79
Pg. 81 - 85
Thinking Physic-ly
Practice Problems #13-16, 17-20, 21-24, 27-31
Reviewing Concepts #1, 6
Applying Concepts #5, 8,
Problems #10, 14, 16, 18, 28