Name: ______________________________________________________ Period: ______ Date: ________________
EMM 12.1
Draw a diagram of each of the different types of pulleys. Show how the string will go
through the pulley by using a colored pen or pencil and include an arrow for the direction
of the pull. In the bottom box, write your hypothesis (If, then, because statement) on how
the pulley will affect effort force and work.
Single Fixed Pulley
H:
Single Fixed, Single Movable Pulley
H:
Double Fixed, Single Movable Pulley
H:
Double Fixed, Double Movable Pulley
H:
Name ________________________________________ Date _______________ Period _____________
Inquiry 12
Read EMM pg 108-115.
1. What is a pulley?
2. How do pulleys help lift loads?
3. What determines how heavy a load a pulley can lift?
Follow the procedures on pg 112-115 to construct the two pulley assemblies and carry out the activity.
Load force:
Type of Pulley
System
Single fixed
Single fixed, single
movable
Double fixed,
single movable
Double fixed,
double movable
5N
Load distance:
Effort Force (N)
Effort Distance (m)
0.1 m
Input Work (N-m)
5N
0.1 m
.5 Nm
2.5N
0.2 m
.5 Nm
2.5 N
0.2 m
.5 Nm
1.2 N
0.4 m
.5 Nm
4. What did you observe about the effort force with the different pulley combinations?
Effort force decreased with the addition of each moveable pulley
5. What happened to effort distance as you changed the pulley systems?
Effort distance increased with the addition of each moveable pulley
Calculations
6. What do your data tell you about the relationship between effort force and effort distance?
As effort force decreases, effort distance increases
7. Look at the input work done for each trial. Is it the same or different? Explain.
Work remains roughly the same because the same load is lifted to the same
height each time. The differences in effort force and effort distance offset each
other.
8. Did the load force change each time? Explain.
No. Each pulley system was lifting the same weight.
9. Did the work done to lift the load change each time? Explain.
No. The effort force was easier (less) but the amount the string needed to be
pulled (distance) was longer each time the moveable pulley was added. Adding
another fixed pulley does not change anything but the direction.
10. Calculate the ideal mechanical advantage of the double-fixed double-moveable pulley system
Ideal MA = ED/LD
ED= 0.4 m
LD = 0.1 m
0.4 m ÷ 0.1 m = 4
11. Calculate the actual mechanical advantage of the double-fixed double-moveable pulley system
Actual MA = LF/EF
.5N ÷ 1.2N = 4.2
LF = 5 N
EF = 1.2 N
12. Calculate the actual mechanical advantage of the double-fixed single-moveable pulley system
Actual MA = LF/EF
LF = .5
EF = 2.5
5 N ÷ 2.5 N = 2