Download Levers Lab

Levers
Purpose: to determine the mechanical advantage of First, Second, and Third Class Levers.
There are 3 classes of levers. In a first class lever, the pivot point or fulcrum is located between the load
(output force, resistance) and your force (input force, effort). What is an example of a first class lever?
In a second class lever, the resistance is between the effort and the fulcrum. What is an example of a second
class lever?
In a third class lever, the effort is between the resistance and the fulcrum. What is an example of a third
class lever?
The mechanical advantage of a lever can be found in the ratio of the force of the resistance to the force of the
effort.
MA = FR
The resistance force is the weight of the object being lifted.
FE
The effort force is the reading on the spring scale.
Procedures:
First Class Lever
1. Place a knife edge holder at the 30 cm mark and put on fulcrum.
2. Place one of the knife edge holders at the 10 cm mark. Put a 500 g weight on the holder.
3. Place a second holder at the 60 cm mark and attach the spring scale. Pull down on the spring scale until
the meter stick is level. RECORD the force reading on the scale.
4. Move the spring scale and holder to the 80 cm mark. Pull down on the spring scale until the meter stick is
level. RECORD the force reading on the scale.
5. Move the spring scale and holder to the 100 cm mark (or as close as you can get it). Pull down on the
spring scale until the meter stick is level. RECORD the force reading on the scale.
Second Class Lever
1. Move the fulcrum and knife edge holder to the 0 cm mark on the meter stick. Move the 500 g mass and
holder to the 30 cm mark.
2. Turn the other holder upside down and place at the 60 cm mark on the meter stick. Pull up on the spring
scale until the lever is level. Record the force reading on the scale.
3. Move the spring and holder to the 80 cm mark. Pull up on the spring scale until the lever is level.
Record the force reading on the scale.
4. Move the spring and holder to the 100 cm mark. Pull up on the spring scale until the lever is level.
Record the force reading on the scale.
Third Class Lever
1. Move the 500 g mass and holder as close to the 100 cm mark as possible. Place the fulcrum and holder at
the 10 cm mark.
2. Place the spring scale and holder at the 40 cm mark. Pull up on the spring scale until the lever is level.
Record the reading on the spring scale.
3. Move the spring scale and holder to the 60 cm mark. Pull up on the spring scale until the lever is level.
Record the reading on the spring scale.
4. Move the spring scale and holder to the 80 cm mark. Pull up on the spring scale until the lever is level.
Record the reading on the spring scale.
Name _____________________________
Partner ______________________ Date __________
DATA TABLE
First Class
60 cm
Second Class
60 cm
Third
40 cm
80 cm
80 cm
60 cm
100 cm
100 cm
80 cm
Class
Analysis
1. Determine the weight of the 500 g mass. Remember: Convert the grams to kilograms AND THEN
multiply by 9.8 m/s2.
2. Calculate the mechanical advantage for each type of lever at each distance.
First Class
MA
Second Class
MA
Third Class
60 cm
60 cm
40 cm
80 cm
80 cm
60 cm
100 cm
100 cm
80 cm
MA
Conclusion
1. Which situation has the greatest mechanical advantage?
Post Lab:
1. Determine the force needed to cause a 3.5 kg mass to accelerate at 4.5 m/s2.
2. How much kinetic energy does an object have if its mass is 10.5 kg and its velocity is 5 m/s?
3. How much work is done when an object with a mass of 50 kg requires 1000 newtons to lift 4 m?
4. What is the mass of an object that has an acceleration of 2.5 m/s2 when 300 N acts on it?