IPC 4a
Calculate speed, momentum, acceleration, work, and power in
systems such as in the human body, moving toys, and machines;
On the left side: The
formula is given in words
Density =
mass
volume
On the right side: The
formula is given in
symbols
D=
m
v
Formula Chart
Formulas
Power = work = force x distance
time
time
Gravity
Constants, Symbols
and Units
Newton’s 2nd Law
TRIANGLE METHODStudent Practice: Scrap Paper
An object has a density of
10 g/cm3 and a volume of
3 cm3. What is its mass?
Answer: 30g
D = m/v
M
÷
D
X
An object has a mass
of 50 g and a volume of
10 cm3. What is its
density?
Answer: 5g/cm3
V
An object has a mass
of 50 g and a density
of 5 g/cm3. What is its
volume?
Answer: 10cm3
TRIANGLE METHOD
Student Practice: Scrap Paper
An object has a mass of
5g and an acceleration of
8 kg/s2 . What force
does it exert?
f = ma
Answer: 40N
f
÷
m
X
An object exerts a force of
100N and has a mass of 50
kg . What is its
acceleration?
Answer: 2kg/ s2
a
An object has a force
of 200N and an
acceleration of 2kg/
s2. What is its mass?
Answer: 100 kg
Triangle Method-Your Turn
• Speed = distance/time (v=d/t)
• Power = work/time (p=w/t)
Student Practice:
Scrap Paper
• Velocity of a wave=frequency x
wavelength (v=fλ)
• Current = voltage/resistance (I = v/R)
d
v
w
t
P
v
v
t
f
λ
I
R
When solving a problem--• First read the problem carefully and list
what you know and what you are solving
for.
• Second identify the formula from the
formula chart that includes what you
are given.
• Third Using the triangle method, set up
the formula. You may have to rearrange
the formula to solve for the unknown
quantity.
Which formula?
• The weight lifter used a force of 980 N to
raise the barbell 2.04 m over her head in
5.21 seconds. Approximately how much work
did she do in raising the barbell?
Work = force x distance
• Approximately how much power did the
weight lifter exert lifting the barbell in 5.21
seconds?
Power = Work/time
• What is the momentum of a 40 kg bike
riders moving at 45 km/h? Momentum = mass x velocity
• What is the mass of a 500.00 mL sample of
seawater with a density of 1.025 g/mL?
Density = mass/volume
Which of the following weightlifters does the
most work on a 100-pound barbell when lifting
the barbell over his or her head? Force
A. A weightlifter who is 5 feet 8 inches tall
B. A weightlifter who is 6 feet 0 inches tall
C. A weightlifter who is 6 feet 2 inches tall
D. A weightlifter who is 6 feet 4 inches tall
From formula chart
Distance
Power
=
work
=
force
x
distance
To decrease power
then work must
time
time
decrease or time
increase.
To decrease work you must decrease the
force or decrease the distance
Which of the following changes would not
increase power?
A. A decrease in the time it takes to do work.
B. A decrease in the distance over which a
force is applied
C. An increase in the force applied
D. An increase in the work added
From formula chart
When solving a problem--• First read the problem carefully and list
what you know and what you are solving
for.
• Second identify the formula from the
formula chart that includes what you
are given.
• Third Using the triangle method, set up
the formula. You may have to rearrange
the formula to solve for the unknown
quantity.
WHAT FORMULA??
• Get out your white board and a dry erase
marker
• We will play a game called “What Formula”
• When you are shown the problem, look at your
formula chart and select the formula you would
use to solve the problem
• Write the formula on your white board and turn
it so your teacher can see it. (You DON’T need
to solve the problem)
What Formula?
V = d/t
Speed =
distance
traveled/time
What Formula?
P=w/t
Power =
work/time
What Formula?
KE = mv2/2
Kinetic
Energy = ½
(mass x
velocity2)
What Formula?
p=mxa
Momentum =
mass x
acceleration
What Formula?
V = d/t
Speed =
distance
traveled/time
What Formula?
F = m/a
Force =
mass/
acceleration
What Formula?
a = vf-vi/∆t
Acceleration
= final
velocity –
initial
velocity/
change in
time
What Formula?
V = d/t
Speed =
distance
traveled/time
What Formula?
P=w/t
Power =
work/time
What Formula?
F = m/a
Force =
mass/
acceleration
What Formula?
a = vf-vi/∆t
Acceleration
= final
velocity –
initial
velocity/
change in
time
What Formula?
V = d/t
Speed =
distance
traveled/time
Density
Foldable
We will now
make a Density
foldable
Density Foldable
m=D x v
D=m/v
V=m/D
g=g/cm3 x cm3
g/cm3=g/cm3
DENSITY
FORMULA
UNITS
Cm3=g/g/cm3
SAMPLE PROBLEMS & SOLUTIONS
Inside Foldable
Definition Under Flap
Density is the amount of mass in a given
volume
D=m/v; v=m/D; m=D x v
FORMULA
UNITS
SAMPLE PROBLEMS
GOOD LUCK!!!!