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# Simple Machine Matching - PowerPoint PPT Presentation

Simple Machine Matching. 1 st Class Lever. 2 nd Class Lever. Slide. Hockey Stick. 3 rd Class Lever. Axe. Inclined Plane. Pulley. Door knob. Nutcracker. Screw. Crane. Wedge. Wheel and Axle. Hand Brakes. Drill. Types of Machines. Chapter 4 Section 3. Levers.

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## PowerPoint Slideshow about 'Simple Machine Matching' - odetta

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Presentation Transcript

1st Class Lever

2nd Class Lever

Slide

Hockey Stick

3rd Class Lever

Axe

Inclined Plane

Pulley

Door knob

Nutcracker

Screw

Crane

Wedge

Wheel and Axle

Hand Brakes

Drill

Chapter 4 Section 3

• A lever is a simple machine consisting of a bar that pivots at a fixed point, called a fulcrum.

• Levers are used to apply a force to a load.

• There are 3 classes of lever, based on the location of the fulcrum, the load, and the input force:

• First, Second, and Third Class

Output force

fulcrum

First Class Levers

• The fulcrum is between the input force and the load.

• Depending on the location of the fulcrum, they can be used to increase force or to increase distance.

input force

Output force

fulcrum

The fulcrum is closer to the load than the input force, so the mechanical advantage isgreater than one. The output force is increased because it is exerted over a shorter distance.

The fulcrum is exactly in the middle, so the mechanical advantage is one. The output force is not increased because the input force’s distance is not increased.

The fulcrum is closer to the input force than to the load, so the mechanical advantage is less than one. Although the output force is less than the input force, a gain in distance occurs.

• The load is between the fulcrum and the input force.

• They do not change the direction of the input force, but they allow you to apply less force than the force exerted by the load.

• Because the output force is greater than the input force, you must exert the input force over a greater distance.

Output force

Input force

fulcrum

Using a 2nd class lever results in a mechanical advantage that is greater than one. The closer the load is to the fulcrum, the more the force is increased and the greater mechanical advantage.

Input force

input force

Output force

fulcrum

• The input force is between the fulcrum and the load.

• They do not change the direction of the input force and they do not increase the input force.

• The output force is always less than the input force.

Input force

Output force

fulcrum

Using a 3rd class lever results in a mechanical advantage of less than one because force is decreased. But, they are helpful because they increase the distance through which the output force is exerted.

Input force

input force

Output force

fulcrum

• An inclined plane is a simple machine that is a straight, slanted surface.

• It allows you to apply a smaller force over a greater distance.

.6 m

.6 m

6 m

MA= 6 m = 10

0.6 m

MA= 3 m = 5

0.6 m

The longer the inclined plane is compared to the height, the greater the mechanical advantage.

Input force

Output force

• A wedge is a double inclined plane that moves.

• It applies an output force that is greater than your input force, but you apply the input force over a greater distance.

• The greater the distance you move the wedge, the greater the force it applies on the object.

MA= 8 m = 4

2 m

2 m

8 m

1 m

10 m

The longer and thinner the wedge is, the greater the mechanical advantage.

MA= 10 m = 10

1 m

Input force

Output force

• A screw is an inclined plane that is wrapped in a spiral.

• When rotated, a small input force is applied over the long distance along the inclined plane (by you) AND the screw applies a large output force through the short distance it is pushed.

• If you could “unwind” the inclined plane of a screw, you would see that it is very long and has a gentle slope.

• The longer the inclined plane is compared to the height, the greater the mechanical advantage.

Input force

Output force

• A wheel and axle is a simple machine consisting of two circular objects of different sizes.

1) When a small input force is applied to the wheel, it rotates through a circular distance.

Input force

2) As the wheel turns, so does the axle. But because the axle is smaller than the wheel, it rotates through a smaller distance, which makes the output force larger than the input force.

wheel

axle

Input force

Output force

MA= 15 cm = 5

3 cm

• A pulley is a simple machine consisting of a grooved wheel that holds a rope or a cable.

• A load is attached to one end of the rope, and an input force is applied to the other end.

• There are two kinds of pulleys:

• Fixed and moveable

• A pulley that only changes the direction of a force. They do not increase the force.

• They are attached to something that does not move.

A fixed pulley only spins. So the distance through which the input force and output force are exerted are the same. So the mechanical advantage is one.

Input force

Output force

• They are attached to the object being moved and they do not change a force’s direction.

A movable pulley moves up with the load as it is lifted. The output force is multiplied because the combined input force is exerted over twice the distance of the output force.

Input force

Output force

• A fixed and movable pulley are used together. Where are they?

• The more pulleys that are used, the greater the mechanical advantage.

The mechanical advantage of this block and tackle is 4 because there are 4 rope segments that support the load. This multiplies your input force 4 times, but you have to pull the rope 4 m just to lift the load 1 m.

Input force

Output force

• Compound machines are machines that are made of two or more simple machines. Where are the simple machines?

• The more moving parts, the less mechanical efficiency. WHY?

• How can we help improve the efficiency?