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A chisel is a very useful tool for carving wood, rocks, and other hard substances. This boy is using a chisel to split pieces of wood from a log. A chisel is a type of machine called a wedge.

What Is a Wedge?

A wedge is simple machine that consists of two inclined planes, giving it a thin end and thick end, as you can see in the Figure of a wedge below . A wedge is used to cut or split apart objects. Force is applied to the thick end of the wedge, and the wedge, in turn, applies force to the object along both of its sloping sides. This force causes the object to split apart.

A knife is another example of a wedge. In the Figure below , a knife is being used to chop tough pecans. The job is easy to do with the knife because of the wedge shape of the blade. The very thin edge of the blade easily enters and cuts through the pecans. You can see other examples of wedges, as well as a history of the wedge, at the following URL:

http://www.historyforkids.org/scienceforkids/physics/machines/wedge.htm

Mechanical Advantage of a Wedge

The mechanical advantage of a simple machine is the factor by which it multiplies the force applied to the machine. It is the ratio of the output force to the input force. A wedge applies more force to the object (output force) than the user applies to the wedge (input force), so the mechanical advantage of a wedge is greater than 1. A longer, thinner wedge has a greater mechanical advantage than a shorter, wider wedge. With all wedges, the trade-off is that the output force is applied over a shorter distance, so force may need to be applied to the wedge repeatedly to push it through the object.

Q : Which wedge in the Figure below do you think would do the same amount of work with less input force?

A : The wedge on the left has a greater mechanical advantage, so it would do the same amount of work with less input force.

Summary

  • A wedge is a simple machine that consists of two inclined planes, giving it a thin end and thick end. Force is applied to the thick end of the wedge, and the sloping sides of the wedge apply force to the object, cutting it or splitting it apart.
  • A wedge makes work easier by increasing the force applied to the object, although it applies the force over a shorter distance. This gives the wedge a mechanical advantage greater than 1.

Vocabulary

  • wedge : Simple machine that consists of two inclined planes.

Practice

At the following URL, click on the wedge to view the animation. Then answer the questions below.

http://www.cosi.org/downloads/activities/simplemachines/sm1.html

  1. How is the mechanical advantage of a wedge calculated in the animation?
  2. Use this method to calculate the mechanical advantage of the wedge shown in the Figure below .
  3. What is the maximum distance a wedge can penetrate an object when the thick end of the wedge is struck?
  4. Why is a wedge one of the least efficient simple machines?

Review

  1. What is a wedge?
  2. How does a wedge change the force applied to it?
  3. Which of the following machines includes a wedge?
    1. axe
    2. hammer
    3. bolt
    4. file
  4. Explain why the mechanical advantage of a wedge is greater than 1.

Vocabulary

wedge

wedge

Simple machine that consists of two inclined planes.

Image Attributions

Description

Difficulty Level:

At Grade

Concept Nodes:

Grades:

7 , 8

Date Created:

Nov 01, 2012

Last Modified:

Nov 12, 2014
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SCI.PSC.222.62.L.1

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