CP PHYSICS
VELOCITY AND ACCELERATION REVIEW
Answer Key
1.
What three components do all good graphs have?
1. Title (usually y-axis label vs. x-axis label)
2. Labeled axes with units
3. Regular intervals for the scales on each axis
2.
Define each of the following terms. State whether they are scalar or vector quantities.
3.
a.
distance: scalar, how far an object travels
b.
displacement: vector, how far an object is from a reference point (starting point)
c.
speed: scalar, how fast an object moves
d.
velocity: vector, the speed and direction of an object that is moving
e.
acceleration: vector, how fast an object’s velocity changes
Identify the following variables and give their units:
d = displacement, m
v = velocity, m/s
t = time, s
a = acceleration, m/s2
vo = initial velocity, m/s
vf = final velocity, m/s
4.
A woman drives 10 miles to work. She returns home for lunch and then drives back to the
office after lunch. What is her total displacement from home? What is the total distance
she drove?
Total displacement = 10 miles (from a reference point – home)
Total distance = 30 miles (10 mi to work, 10 mi to home, 10 mi to work)
5.
When does an object experience acceleration?
An object only experiences acceleration when it changes speed, changes its
direction, or changes both speed and direction.
6.
If a car travels around a circular track at 22 km/h, is the car’s motion described as
uniform or accelerated? Explain!
Its motion is described as accelerated since it is always changing direction even
`
if it maintains a constant speed of 22 km/h.
7.
If an object is said to have uniform motion, then what does one know about its velocity?
about its acceleration?
An object with uniform motion has a constant velocity. It has no acceleration
since constant velocity means the object’s speed and direction remain the same.
8.
Draw all motion graphs that represent no motion or zero velocity.
CP PHYSICS, VELOCITY AND ACCELERATION REVIEW, page 2
Answer Key
9.
Draw all motion graphs that represent uniform motion or constant velocity.
10.
Draw all motion graphs that represent constant acceleration?
11.
What value does the slope of a displacement-time graph represent?
12.
What value does the slope of a velocity-time graph represent? acceleration
13.
How can displacement be determined using a velocity-time graph?
Find the area under the line for the given time interval.
NOTE: It is extremely helpful to shade in the specified area to determine its shape.
14.
What does “g” represent in equations? What is its value?
g = acceleration due to gravity, value = 9.8 m/s2
15.
What is the initial velocity of all objects that fall?
0 m/s
16.
What values do all falling objects have in common? (Assuming no air resistance.)
a = 9.8 m/s2 and vo = 0 m/s
17.
Graph the following data and answer the questions below.
Time (s)
0
2
5
6
7
8
10
12
14
Velocity (m/s)
20
20
20
30
35
40
30
15
0
velocity
CP PHYSICS, VELOCITY AND ACCELERATION REVIEW, page 3
17.
a.
Answer Key
What is the displacement of the object at 5 seconds?
l x w = (5)(20) = 100 m
b.
What is the object’s displacement between 10 and 14 seconds?
½ bh = ½ (4)(30) = 60 m
18.
Solve the following problems. Use GUESS and show all work!!!!!!! Circle your answers.
a.
After 16.5 s, a jogger’s displacement is 200.0 m. What is her average velocity in
m/s? in km/h?
v=?
v = d = 200
d = 200.0 m
t
16.5
t = 16.5 s
v = 12.12 m/s x 3.6 = 43.63 km/h
b.
How long would it take a car to travel 6.0 km if its speed is a constant 30.0 km/h?
v = 30.0 km/h
t = d = 6.0
d = 6.0 km
v
30.0
t=?
t = 0.2 s
c.
Find the distance a bicyclist travels in 0.75 h if she is traveling at a constant speed
of 20.0 km/h.
v = 20.0 km/h
d = vt = (20.0)(0.75)
d=?
d = 15 km
t = 0.75 h
d.
What is the acceleration of a car traveling in a straight line at constant speed of
80 km/h?
It has zero acceleration since neither its speed nor direction is changing.
e.
The Road Runner steps off a ledge and drops to the ground in 0.50 s.
1. What is the Road Runner’s velocity the instant before he hits the ground?
vo = 0 m/s
vf = vo + at
vf = ?
= 0 + (9.8)(0.50)
d=
vf = 4.9 m/s
a = 9.8 m/s2
t = 0.50 s
2. How high is the ledge off the ground?
vo = 0 m/s
d = vot + ½ at2
vf =
= (0)(0.50) + ½ (9.8)(0.502)
d =?
d = 1.23 m
a = 9.8 m/s2
t = 0.50 s
f.
A race car accelerates from rest at a rate of +7.5 m/s2 for 4.5 s. How fast will it be
going at the end of that time?
vo = 0 m/s
vf = vo + at
vf = ?
= 0 + (7.5)(4.5)
d=
vf = 4.9 m/s
a = 7.5 m/s2
t = 4.5 s
CP PHYSICS, VELOCITY AND ACCELERATION REVIEW, page 4
Answer Key
g.
A race car starts from rest and is accelerated uniformly to +41 m/s in 8.0 s. What
is the car’s displacement?
vo = 0 m/s
d = ½ (vf + vo)t
vf = 41 m/s
= ½ (41 + 0)(8)
d =?
d = 164 m
a=
t = 8.0 s
h.
A motorcycle traveling at 16 m/s accelerates at a constant rate of 4.0 m/s2 over
50 m. What is its final velocity?
vo = 16 m/s
vf2 = vo2 + 2ad
vf = ?
vf2 = 162 + 2(4)(50)
d = 50 m
= 256 + 400
a = 4.0 m/s2
vf2 = 656
t=
vf = 25.61 m/s
i.
A hockey player skating at 3 m/s comes to a complete stop in 5.0 m. What is the
acceleration of the hockey player?
vo = 3 m/s
vf2 = vo2 + 2ad
vf = 0 m/s
02 = 32 + 2(a)(5)
d = 5.0 m
0 = 9 + 10a
a=?
-9 = 10a
t=
10
10
a = -0.9 m/s2
j.
A lab cart travels at 0.25 m/s and is then accelerated at a constant rate to a
velocity of 1.25 m/s. If the acceleration lasts for 4.2 s, what is the cart’s
acceleration?
vo = 0.25 m/s
vf = vo + at
vf = 1.25 m/s
1.25 = 0.25 + (a)(4.2)
d=
1 = 4.2a
a=?
4.2 4.2
t = 4.2 s
a = 0.24 m/s2
k.
A tennis ball is dropped from a bridge that is 44 m high.
1. How long before it hits the ground below?
vo = 0 m/s
d = vot + ½ at2
vf =
44 = ½ (9.8)t2
d = 44 m
44 = 4.9t2
a = 9.8 m/s2
4.9 4.9
t=?
t2 = 8.98
t = 3.0 s
2. How fast will it be moving just before it hits?
vo = 0 m/s
vf2 = vo2 + 2ad
vf = ?
vf2 = 02 + 2(9.8)(44)
d = 44 m
vf2 = 862.4
2
a = 9.8 m/s
vf = 29.37 m/s
t=