FORMULA’S:
Name: ________________________________8___
LEARNING OUTCOME #3: Investigate and describe the transmission of force and energy between parts of
a mechanical system
3a) analyze mechanical devices to determine speed ratios and force ratios
3c) compare theoretical and actual values of force ratios, and propose explanations for discrepancies
Machines are used to make work easier.
CALCULATING MECHANICAL ADVANTAGE: The mechanical advantage is the amount
by which a machine can _____________ a force.
Mechanical Advantage (MA) = _____________
MA = OF
IF
Using the pulley system setup:
MA = _____
MA = _____
MA = ______
What does this 4 mean? The Mechanical Advantage of 4 means:
that the pulley system will _____________________________________
________________________________________________________________
So if the input force to the pulley system was 100N the pulley
system would be able to lift (________N X ____) a ______N load.
CALCULATING SPEED RATIO: Speed Ratio is another way of analyzing how machines
work. Speed measures the __________________________________________________________
_____________________________________________________________________________________
Speed Ratio (SR) = _________________
SR = ID
OD
Using the same pulley system setup, but measuring distance
instead.
SR = _____
SR = _____
SR = ____
What does this mean? The Speed Ratio means that the ________
________________________________________________________________
So if the output force moved 5m the input force would have to
move (____m X ____) _____m!
IF YOU NOTICED THE MA EQUALS THE SR FOR THE SAME DEVICE!!!
Calculate the following Mechanical Advantage and Speed Ratio for each device used!
MECHANICAL ADVANTAGE
SPEED RATIO
1 Calculate the mechanical advantage
This mechanical device has an input
when it takes 200N to move a 550N
distance of 45m and an output distance of
object.
15m.
2 Hans made a tree branch trimming
machine to help clean up his yard. The
input effort to the machine was 2.7N
but the output was 6N.
Hans’s tree branch trimming machine
needs to be moved 0.5m to cut a distance
of 0.2m.
3 Robert invented a machine that would
do his work for him. His machine used
5.6N and produced 11N.
Robert’s machine moves 2.3m when the
input force moves 5m.
4 Arnold built a machine to help deliver
the morning paper. He had to pull with
38N of force to move a stack of papers
that had a force of 92N.
Arnold’s machine moves the load 1.8m
when the input distance is 6.2m.
Does the MA = SR for the above devices? _______
What do you think accounts for the difference?
So Mechanical Advantage will always be __________________ than Speed Ratio!
5. Can the mechanical advantage of a device be less than one? pg 282 Think of a
bicycle. It has a mechanical advantage of less than one! Why do we use them then?
6. Mechanical Advantage is always LESS THAN Speed Ratio because Mechanical
Advantage is affected by _____________________. Mechanical Advantage is more
realistic than Speed Ratio.
7. We now want to look at the EFFICIENCY of the device.
EFFICIENCY means: the measurement of how well a machine uses the input
energy. Efficiency is measured as a percentage!
EFFICIENCY = _________________________________
Eff = MA
SR
X 100
8. Calculate the efficiency of the machines in questions 1-4 (formula, substitute in,
answer with units)
#1
Eff = MA X 100
Eff = _____ X 100
SR
Hans
Robert
Arnold
9. THE MORE ENERGY THAT IS LOST BY A MACHINE DUE TO FRICTION
( AS __________) THE LESS EFFICIENT IT IS! Less input energy converted to
output energy!
10. Can a machine be 100% efficient? Explain.
2.2 The Science of WORK!! Page 287
1. Work is done: when a __________________ acts on an object to make it _____________.
If the object DOES NOT MOVE—no work is done!
WORK = ____________(N) x _______________(m)
Units for WORK: N·m
W=Fd
(1N·m = 1 JOULE)
2. If you used 50N to lift a chair 0.4m, what is the amount of work done?
W=Fd
W= ____N x ____m
W= ____N·m or ____Joules
3. You used a force of 40N to push a box of books 3.2m. How much work has been
done?
4. A pulley uses 1000N to lift a piano up 10m. How much work is being done?
5. a. Calculate the amount of work needed to lift the box up onto the loading dock
(known as WORK OUTPUT).
800N
2m
b. Calculate the amount of work needed to push the box up onto the loading dock
using the incline plane. (known as WORK INPUT)
c. Is there any difference in the amount of work done in (a) and (b) to get the box to
the top of the loading dock? Yes or No
In either case the WORK INPUT = WORK OUTPUT
d. Why would pushing the box up the loading dock seem easier?
FORMULA CALCULATIONS: FORMATIVE ASSESSMENT
Name: ____________________________ 8___
Date: ________________
LEARNING OUTCOME #3: Investigate and describe the transmission of force and energy between parts
of a mechanical system
3a) analyze mechanical devices to determine speed ratios and force ratios
3c) compare theoretical and actual values of force ratios, and propose explanations for discrepancies
3d) identify work input and work output in joules for a simple machine or mechanical system
a. Place the following data onto the simple machine diagram.
-input force: 70N
-output force: 200N
-input distance: 30m
-output distance: 10m
b. This simple machine is called a
____________________________
and the advantage you would get is
__________________________________.
c. Calculate mechanical advantage.
d. Calculate the speed ratio.
e. Why is the speed ratio and mechanical advantage different?
f. Calculate the efficiency for this simple machine.
g. Why is this machine not 100% efficient?
h. Calculate the work done by this simple machine. Be careful on what data you use!
Beginning
 demonstrates limited
academic achievement
 shows an incomplete
understanding of the
learning
Acceptable
Proficient
 demonstrates basic academic
achievement
 shows an adequate
understanding and simplistic
application of the learning
 demonstrates strong academic
achievement
 shows a solid understanding and
relevant application of the
learning
Mastery
 demonstrates exemplary
academic achievement
 shows an in-depth understanding
and insightful application of the
learning in a variety of situations
2.3 Hydraulics
Page 293
We have already looked at hydraulics in the Mix and Flow unit. Remember that
hydraulics lift/move very large loads.
A hydraulic system uses _______________ under ___________________ to move loads. The
hydraulics _______________ the mechanical advantage of levers. Before hydraulics were
invented, construction projects were mainly done by _____________, using ______________
__________________ (inclined planes, _______________, _____________ and ____________)
P = F/A
P = _________________ F = _______________ A = ________________
Pascal’s Law: pressure applied to an enclosed fluid is transmitted
__________________ in _______ _______________ throughout the fluid.
Hydraulics use a fluid such as ___________
Pneumatics use a fluid such as ___________
Calculate the mechanical advantage of the hydraulic below.
20N
500N
FORMULAS:
W=Fd
Eff = MA X 100
SR
SR = ID
OD
MA = OF
IF