Second-Class Levers
In a second-class lever the output force is located between the input force and the fulcrum. The wheelbarrow shown in Figure 13B is a second-class lever.
When you lift the handles of a wheelbarrow, it rotates around its fulcrum. Parts of the wheelbarrow near the fulcrum move through a smaller distance than those closer to the handle. Thus the input distance your hands move to lift the wheelbarrow is larger than the output distance the wheelbarrow moves to lift its load. The increased input distance means it takes less force from you to lift the load. The mechanical advantage of a second-class lever is always greater than 1.
Third-Class Lever
The input force of a third-class lever is located between the fulcrum and the output force. As shown in Figure 13C, the output distance over which the third-class lever exerts its force is always larger than the input distance you move the lever through. Because of this, the mechanical advantage of a third-class lever is always less than 1. Baseball bats, hockey sticks, and golf clubs are all third-class levers.
Which classes of levers can have a mechanical advantage less than 1?
Quick Lab
Comparing Lever Arms
Materials
pencil, masking tape, spring scale, 500-g mass, meter stick
Procedure 
Construct a data table with columns labeled Output Force, Output Arm, Input Force, Input Arm, and Mechanical Advantage.
Suspend the 500-g mass from the spring scale. Observe the force on the scale and record it as the output force.
Tape a pencil parallel to and near the edge of a table as shown. Tape the 500-g mass to the meter stick so it's centered on the 10-cm mark.
Position the 20-cm mark of the meter stick on the pencil as shown. Record the distance from the pencil to the center of the mass as the output arm.
Attach the spring scale at the 90-cm mark of the meter stick. Record the distance from the pencil to this mark as the input arm.
Pull straight down on the spring scale so the 500-g mass is lifted off of the table. Record the force on the spring scale as the input force.
Repeat Steps 5 and 6 with the spring scale located at the 80-cm, 70-cm, 60-cm, and 50-cm marks on the meter stick.
Analyze and Conclude
Calculating Calculate and record the mechanical advantage of the lever for each input arm.
Using Graphs Plot a graph of mechanical advantage versus the length of the input arm.
Analyzing Data How does changing the input arm affect the mechanical advantage?
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