Understanding Levers - Grade 7

What is a “lever”?

Answer explanation

A simple machine that helps lift or move heavy objects with less effort, using a fulcrum (pivot point) to change the direction or amount of force.

What is a first class lever? Explain.

Answer explanation

A first-class lever is a simple machine with the fulcrum, or pivot point, positioned in the middle. This setup allows for a change in direction or amount of force, making tasks easier. When you apply force, or effort, on one side of the lever, the other side moves, lifting or moving the load. The fulcrum's central location enables you to use less effort to accomplish more, demonstrating the mechanical advantage of first-class levers.

Draw a first class lever.

Answer explanation

This is an example. Any other example that expresses the same idea will be marked correct.

What is a second class lever? Explain.

Answer explanation

A second-class lever makes lifting easier by positioning the fulcrum at one end. The load, or object to be lifted, is placed between the fulcrum and where you apply force (effort). When you push or pull the effort end, the load moves, making it simpler to lift heavier objects. This setup multiplies the force, allowing you to accomplish more with less effort, illustrating the mechanical advantage of second-class levers.

Draw a second class lever.

Answer explanation

This is an example. Any other example that expresses the same idea will be marked correct.

What is a third class lever? Explain.

Answer explanation

A third-class lever has the fulcrum at one end. The effort is applied in the middle, and the load is at the other end. This setup helps move the load faster and farther, but doesn't make it easier to lift. Instead, it gives more control over the load's movement.

Draw a third class lever.

Answer explanation

This is an example. Any other example that expresses the same idea will be marked correct.

List 3 examples of levers that are used in our daily lives.

Answer explanation

First-Class Levers:

1. Scissors

2. Pliers

3. Seesaws

4. Door handles

5. Wheelchairs (brake lever)

Second-Class Levers:

1. Wheelbarrows

2. Nutcrackers

3. Bottle openers

4. Lawn mowers (lever to adjust height)

5. Garage door openers

Third-Class Levers:

1. Hammers

2. Fishing rods

3. Baseball bats

4. Golf clubs

5. Shovels

Other Examples:

1. Lever faucets (kitchen and bathroom)

2. Gearshift levers (cars)

3. Brake levers (bicycles)

4. Clamps

5. Crowbars

Study the image and identify which method is the first, second and third class lever. Explain your reasons for identifying the lever class to be a specific method shown in the image.

Answer explanation

The first class lever has the fulcrum in the middle (e.g., seesaw), the second class lever has the load in the middle (e.g., wheelbarrow), and the third class lever has the effort in the middle (e.g., tweezers). This classification is based on their arrangement.

Looking at the image, which method would be easier to lift the box? Give a reason for your answer.

Answer explanation

Lifting the box using a lever would be easier because it reduces the amount of force needed to lift the weight, allowing you to use less effort compared to lifting it directly.