Download Net Force

Do Now
Chart on page 2 of your notes!
Use the following info AND the
info on the board to solve your Do
Now! Either write this down, take
a picture and re-write at
home/later, or take a picture and
print it out…remember, no
phones on Open Notes Quizzes!
Net Force = mass x acceleration
Fnet = m a
Newton’s 2nd Law states that a Net
Force applied to a mass causes a
change in motion (an
acceleration!)
#
Net
Force
(N)
Mass
(kg)
1.
10
2
2.
20
2
3.
20
4
2
4.
5.
10
Acceleration
(m/s2)
5
10
Use this column for work
space if needed
Take out your HW due today…
• Rapid review
• We are popcorning – pay attention!!
Midterm Info
• You are receiving your…
– Frequently asked question sheet
– Cheat sheet
Jan 14th & 15th
• Don’t forget:
– Project!
– Test! (there are 2 links on the test’s Genesis task
that will help you prep for the test)
**Remember**
Fnet = m a
N = kg m
2
s
.
The Newton is an abbreviation!
• What happens if you are solving for
NEWTONS (Force)….
– but are given MASS in GRAMS? (g)
– Or acceleration in miles per hour per second?
Do #4-5
FORCE & ACCELERATION are
0%
er
l
in
fo
to
an
sw
io
na
ug
h
No
tp
po
rti
o
pr
o
ly
se
In
ve
r
0%
ro
po
rt
al
on
or
ti
pr
op
ct
ly
Di
re
0%
na
l
0%
No
te
no
A. Directly
proportional
B. Inversely
proportional
C. Not proportional
D. Not enough info to
answer
MASS & ACCELERATION are
0%
er
l
in
fo
to
an
sw
io
na
ug
h
No
tp
po
rti
o
pr
o
ly
se
In
ve
r
0%
ro
po
rt
al
on
or
ti
pr
op
ct
ly
Di
re
0%
na
l
0%
No
te
no
A. Directly
proportional
B. Inversely
proportional
C. Not proportional
D. Not enough info to
answer
Do #6-7
Two shopping carts of equal mass are pushed by two
different people.
Cart A accelerates four times more than Cart B.
Describe the magnitude or amount of force applied to
Cart A compared to the Cart B.
¼
ha
s
tA
Ca
r
in
fo
0%
...
ug
h
no
No
te
ne
t
th
e
he
4x
t
ha
s
tA
0%
fo
rc
fo
rc
ne
t
ne
t
sa
m
e
th
e
Ca
r
tA
Ca
r
0%
...
f..
.
0%
ha
s
1. Cart A has the same net force as
the Cart B.
2. Cart A has 4x the net force of the
Cart B
3. Cart A has ¼ the net force of the
Cart B
4. Not enough info
Two shopping carts of equal mass are pushed by two
different people.
Cart A accelerates four times more than Cart B.
Describe the magnitude or amount of force applied to
Cart A compared to the Cart B.
Cart A
Fnet = m a
Cart B
Fnet = m a
Force = 1 x 4
Force = 1 x 1
Force = 4
Force = 1
Cart A experiences 4x the force of cart B!
Two shopping carts of different mass are pushed by
two different people, who apply the SAME force.
Cart A accelerates four times more than Cart B.
Describe the mass of Cart A compared to the Cart B.
¼
ha
s
tA
Ca
r
in
fo
0%
ug
h
ft
th
e
he
4x
t
ha
s
tA
0%
..
f..
.
m
as
so
e
sa
m
th
e
ha
s
tA
Ca
r
4. Not enough info
Ca
r
3. Cart A has ¼ the mass of the
Cart B.
m
as
s. .
.
2. Cart A has 4x the mass of the
Cart B.
0%
No
te
no
0%
m
as
so
1. Cart A has the same mass as
the Cart B.
Two shopping carts of different mass are pushed by two
different people, who apply the SAME force.
Cart A accelerates four times more than Cart B.
Describe the mass of Cart A compared to the Cart B.
Cart A
Fnet = m a
Cart B
F net = m a
1=m
1= m
m= 1
4
x
4
x
m=1
Cart 1 has ¼ the mass of cart 2!
1
Newton’s Law Math
• Answer the True/False questions found in #8
• Get your clickers ready
Balanced forces cause constant
acceleration.
1. True
2. False
3. Not quite sure
0%
su
re
se
0%
No
tq
ui
te
Fa
l
ue
0%
Tr
Balanced forces cause
ZERO acceleration.
OR
Unbalanced forces
cause acceleration.
The greater net force applied, the greater
the acceleration.
0%
su
re
se
0%
ui
te
No
tq
Tr
ue
0%
Fa
l
1. True
2. False
3. Not quite sure
A non-zero net force (in other words, a net force
MORE than 0) acting on an object causes
acceleration.
0%
su
re
se
0%
ui
te
No
tq
Tr
ue
0%
Fa
l
1. True
2. False
3. Not quite sure
The forces acting on an object at rest are unbalanced.
The forces acting on an
object at rest are balanced.
OR
The forces acting on an object
changing velocity are
unbalanced.
0%
su
re
se
0%
ui
te
No
tq
Tr
ue
0%
Fa
l
1. True
2. False
3. Not quite sure
Force and acceleration are inversely proportional.
Force and acceleration are directly proportional.
0%
su
re
se
0%
ui
te
No
tq
Tr
ue
0%
Fa
l
1. True
2. False
3. Not quite sure
Mass and acceleration are inversely proportional.
0%
su
re
se
0%
ui
te
No
tq
Tr
ue
0%
Fa
l
1. True
2. False
3. Not quite sure
If you triple the force applied to something, you would expect
1/3 as much acceleration.
If you triple the force applied to something, you
would expect 3X as much acceleration.
0%
su
re
se
0%
ui
te
No
tq
Tr
ue
0%
Fa
l
1. True
2. False
3. Not quite sure
If you triple the force applied to something, you would
expect 3X as much acceleration.
Fnet = m a
1=1 x1
3=1 x3
NOT
3=1 x1
3
(Net Force = mass times acceleration)
#9
• Justin Bieber has a mass of 65 kg. After I kick
him, he accelerates at a rate of 3 m/s2.
– What is the net force acting on Justin?
m = 65 kg
a = 3 m/s2
F=ma
F = 195 N
#10a
• During football practice, two linemen are pushing a
coach on the sled. The combined mass of the sled
and the coach is 300 kg. The sled accelerates at a
rate of 0.580 m/s2.
– What is the net force acting on the on the sled by the
linemen?
m = 300 kg
a = 0.58 m/s2
F=ma
F = 174 N
#10b
• During football practice, two linemen are pushing a coach
on the sled. The combined mass of the sled and the coach
is 300 kg. The sled accelerates at a rate of 0.580 m/s2.
– What if another coach hopped on the sled, doubling the
mass of the coach-sled system? What would be the new
net force (*assuming the acceleration stayed the
same)? (HINT – do you need to do the formula again, or
can you think conceptually using proportions?)
If the F before was 174 N…
Force and mass are DIRECTLY proportional
If there is double the mass, the football players must now
push twice as hard ( double the force) !
New force is double 174 N = 348 N
#11 a
• A student is driving down the road when they see
Miley Cyrus on a wrecking ball. They speed up, and
eventually crash into Miley with a rightward force of
300 N. Miley & her wrecking ball are a combined
150 kg.
– What is Miley & Wrecking Ball’s acceleration?
m = 150 kg
F = 300 N
a = F/m
a = 2 m/s2
#11 b
After the collision, Miley flies off the wrecking ball. Her
mass is only 50 kg. The student drives into her again with a
force of 300 N. What is Miley’s acceleration?
• (HINT – do you need to do the formula again, or can
you think conceptually using proportions?)
If the acc. before was 2 m/s2…
MASS and ACC. are INVERSELY proportional
If there is 1/3 the mass (from 150 kg to 50 kg), there
is now 3x the acceleration!
Acceleration is 6 m/s2
a. THINK CONCEPTUALLY!! Anna Litical and Noah
Formula are experimenting with the effect of mass
and net force upon the acceleration of a lab cart.
They determine that a net force of F causes a cart
with a mass of M to accelerate at 48 cm/s2. What is
the acceleration value of a cart with …
a mass of M when acted upon by a net force of 2F?
0%
ab
o
ve
/s
2
cm
N
on
e
of
th
e
96
cm
72
cm
48
0%
/s
2
0%
/s
2
0%
/s
2
0%
cm
24 cm/s2
48 cm/s2
72 cm/s2
96 cm/s2
None of the above
24
A.
B.
C.
D.
E.
b. THINK CONCEPTUALLY!! Anna Litical and Noah
Formula are experimenting with the effect of mass
and net force upon the acceleration of a lab cart.
They determine that a net force of F causes a cart
with a mass of M to accelerate at 48 cm/s2. What is
the acceleration value of a cart with …
a mass of 2M when acted upon by a net force of F?
0%
ab
o
ve
/s
2
cm
N
on
e
of
th
e
96
cm
72
cm
48
0%
/s
2
0%
/s
2
0%
/s
2
0%
cm
24 cm/s2
48 cm/s2
72 cm/s2
96 cm/s2
None of the above
24
A.
B.
C.
D.
E.
c. THINK CONCEPTUALLY!! Anna Litical and Noah
Formula are experimenting with the effect of mass
and net force upon the acceleration of a lab cart.
They determine that a net force of F causes a cart
with a mass of M to accelerate at 48 cm/s2. What is
the acceleration value of a cart with …
a mass of 2M when acted upon by a net force of 2F?
0%
ab
o
ve
/s
2
cm
N
on
e
of
th
e
96
cm
72
cm
48
0%
/s
2
0%
/s
2
0%
/s
2
0%
cm
24 cm/s2
48 cm/s2
72 cm/s2
96 cm/s2
None of the above
24
A.
B.
C.
D.
E.
d. THINK CONCEPTUALLY!! Anna Litical and Noah
Formula are experimenting with the effect of mass
and net force upon the acceleration of a lab cart.
They determine that a net force of F causes a cart
with a mass of M to accelerate at 48 cm/s2. What is
the acceleration value of a cart with …
a mass of 4M when acted upon by a net force of 2F?
0%
ab
o
ve
/s
2
cm
N
on
e
of
th
e
96
cm
72
cm
48
0%
/s
2
0%
/s
2
0%
/s
2
0%
cm
24 cm/s2
48 cm/s2
72 cm/s2
96 cm/s2
None of the above
24
A.
B.
C.
D.
E.
e. THINK CONCEPTUALLY!! Anna Litical and Noah
Formula are experimenting with the effect of mass
and net force upon the acceleration of a lab cart.
They determine that a net force of F causes a cart
with a mass of M to accelerate at 48 cm/s2. What is
the acceleration value of a cart with …
a mass of 2M when acted upon by a net force of 4F?
0%
ab
o
ve
/s
2
cm
N
on
e
of
th
e
96
cm
72
cm
48
0%
/s
2
0%
/s
2
0%
/s
2
0%
cm
24 cm/s2
48 cm/s2
72 cm/s2
96 cm/s2
None of the above
24
A.
B.
C.
D.
E.
Finish the rest of the questions!
• Whatever is not done is HW (EXCEPT the
challenge problems!)
• However, although the challenge problems
aren't HW, you might see questions like that
as test extra credit, so it would be a good idea
to do them!