machines

What is a simple or compound machine?

A simple or compound machine is a non motorized device that is used to change the magnitude or direction of force.

Simple Notes about machines

There are 6 simple machines.these 6 are the pulley,the lever,the wheel and axel, the wedge,inclined plane, and the screw.all of theses simple machines are used to make every day jobs and problems easier.

Formulas for Machines

Machines make work easier: Multiply force or distance, or change the direction of force. Mechanical Advantage (MA) is the factor by which force is increased. Ideal Mechanical Advantage (IMA) is a "perfect world" result. Actual Mechanical Advantage (AMA) accounts for losses.

• Work = Force x Distance - Work in = Work out • MA = Force out / Force In • MA = Distance In / Distance Out • Force is measured in Newtons (N) (1kg on Earth pulls at 9.81 N) • Distance is measured in Meters (m), Work in N*m (Joules) • Work out / Work in = Efficiency •

pulley

Definition- a wheel with a grooved rim around which a cord passes. It acts to change the direction of a force applied to the cord and is chiefly used (typically in combination) to raise heavy weights.

What is a pulley?

Sometimes it is not easy to lift heavy objects with just human power. A basic pulley comprises of a wheel fixed on an axel with a grrove around the edges to guide the rope or cable.

Load: = the weight of the object you are lifting or moving.

Effort: = the amount of force required to lift or move an object.

Wheel and axle

Definition- a simple lifting machine consisting of a rope which unwinds from a wheel on to a cylindrical drum or shaft joined to the wheel to provide mechanical advantage.

Wheel and axel

The mechanical advantage law in action

What mechanical advantage is provided by a car steering wheel with a diameter of about 600 mm and an axle diameter of about 50 mm? First, knowing that the radius is half the diameter, the radius of the steering wheel is 300 mm (R) and that of the axle is 25mm (r). The mechanical advantage of this system is R/r or in this case 300/25 which equals 12. This means that in theory the effort needed to move a load (the car wheel) is reduced to 1/12 of the weight of the load. Other factors come into play, such as friction, but you can see that there is a real advantage with a system like this.

wedge

Wedge: Triangular shaped, forces 2 objects apart. Must make output force perpendicular to input force. IMA= length of slope divided by width of wedge

Definition:a piece of wood, metal, or some other material having one thick end and tapering to a thin edge, that is driven between two objects or parts of an object to secure or separate them.

Inclined plane

Inclined Plane: an angled surface used to raise or lower a load, uses less force than vertically lifting, but over a greater distance. IMA= ratio of the length of the sloped surface to the height it spans.

Definition:a plane inclined at an angle to the horizontal.

a sloping ramp up which heavy loads can be raised by ropes or chains.

Inclined plane

The inclined plane

An inclined plane is a flat surface set at an angle. The mechanical advantage of an inclined plane is generally high so it is easier to lift or move heavy objects by increasing the distance travelled. Chocking a wedge under a rock with a sledge hammer will eventually move most stubborn boulders, by applying a large force over a short distance. Decreasing the angle of the plane increases the mechanical advantage, while also increasing the distance the object has to travel. The same amount of work is done, but it makes what could be a difficult task easier.

The inclined plane as a ramp

Inclined planes, commonly called ramps, are seen at the entrances to buildings, where a driveway crosses a footpath or as a pathway up a steep slope. Ramps are easier to walk up than steps, and the gentle continuous slope provides easier access for wheelchairs and prams. It's also easier to load heavy objects into a truck for example by leaning a plank from the ground to the back of the truck.

A child's slide is an inclined plane too

In a child's slide the force is controlled in a different way to the plank leaning against the back of a truck. If the child fell from the top of the slide then the force on landing could cause injury. By increasing the distance the child travels, the force is reduced.

Effort versus load

Look at this ramp.

Pushing the load up the ramp means that it moves along a distance that is double the vertical height. The payoff is that the effort required is only half that needed to lift the load vertically the same distance.

The general rule is that a less steep slope means that the object moves further, but the effort is less. The ratio of vertical height to slope distance is equal to the proportional effort needed.

If, in the illustration above, the slope is reduced so that the slope distance is 3 m

Screw

Screw converts rotational motion to linear motion. IMA=ratio of the circumference of the screw to the distance it advances during each revolution

a short, slender, sharp-pointed metal pin with a raised helical thread running around it and a slotted head, used to join things together by being rotated so that it pierces wood or other material and is held tightly in place.

lever

Definition- a rigid bar resting on a pivot, used to help move a heavy or firmly fixed load with one end when pressure is applied to the other.

Lever: Has a fulcrum, load and effort that act on an arm. Further divided into 3 classes: Class 1= seesaw. Fulcrum in center Class 2= wheelbarrow. Load in center Class 3= arm. Effort in center:

the three types of Levers

Class 1= seesaw. Fulcrum in center:

Class 2= wheelbarrow. Load in center:

Class 3= arm. Effort in center:

Class 1= seesaw.

Class 1: Fulcrum in the middle: the effort is applied on one side of the fulcrum and the resistance (or load) on the other side, for example, a seesaw, a crowbar or a pair of scissors.

First class levers have the fulcrum between the force and the load. In using a screwdriver to lift the lid from a paint tin you are moving the effort over a greater distance than the load. By having the fulcrum (the rim of the tin) close to the lid (the load) a larger force can be applied to the load to open the tin. By this means you are reducing the effort required, this is what first class levers do best. Other examples of first class levers are pliers, scissors, a crow bar, a claw hammer, a see-saw and a weighing balance.

Class 2: Wheelbarrow

Class 2= wheelbarrow. Load in center

In second class levers the load is between the effort (force) and the fulcrum. A common example is a wheelbarrow where the effort moves a large distance to lift a heavy load, with the axle and wheel as the fulcrum.

In a second class lever the effort moves over a large distance to raise the load a small distance. As the ratio of effort (force) arm length to load arm length increases, the mechanical advantage of a second class lever increases. In a wheelbarrow, the closer the load is to the wheel, the greater the mechanical advantage. Nutcrackers are also an example of a second class lever.

Class 3: Arm

With third class levers the effort is between the load and the fulcrum, for example in barbecue tongs. Other examples of third class levers are a broom, a fishing rod and a woomera.

In a third class lever the load moves further than the effort (force) and the mechanical advantage is low, which is why it's difficult to apply great force to the load. This can be an advantage by not squashing sausages on the barbecue!

When you lift a load using your forearm you are using a third class lever. Your biceps muscles are attached to the forearm just in front of the elbow. The load is on the hand, and the effort is between the fulcrum (elbow) and the load.

gears

Gears

Gears are typically wheels with teeth or cogs. They are used to transmit effort, change torque (turning force), change direction, or change speed. There are several basic types of gears including:

simple gears

bevel gears

worm gears

rack and pinion

Simple gears

The simplest form is two gear wheels with the teeth meshing. In all gear systems one gear will be powered. This is called the drive gear and the other gear is called the driven gear. In a series of gears, each pair of gears can be considered to consist of a drive gear and a driven gear. If the number of teeth is the same on each gear, then the driven gear rotates at the same rotational speed as the driving gear, but in the opposite direction.

If the driven gear has more teeth than the driving gear, the driven gear rotates at a slower rotational speed.

If the driven gear has less teeth than the driving gear, the driven gear rotates at a faster rotational speed.

The mechanical advantage of a pair of gears is the number of driven gear teeth divided by the number of driving gear teeth.

Also gears

As an example, if the driving gear has 30 teeth and the driven gear 15 teeth, the mechanical advantage is 15/30 = 0.5. Conversely, if the driven gear has 30 teeth and the driving gear 15 teeth the mechanical advantage is 30/15 = 2.

Bikes use gears to increase the efficiency of the rider, depending on the surface and slope being tackled! Bikes are designed to have a mechanical advantage of less than one. That is, the input force of the rider acts over a short distance on the crank wheel gear, pushing the larger rear wheel over a longer distance. As a rider drops down through the gears on riding up a hill, the crank wheel gear is made larger and the rear gear wheel smaller until a MA of 1 is approached on very steep hills. Various mechanical advantages can be achieved by changing the rear and crank gear sizes, commonly know as "changing gears".

Bevel Gears

Bevel gears have teeth set at a 45° angle to the direction of turning. The same rules apply as for standard gears, but the two gear shafts are at right angles. This system of gears is useful to transmit force at a 90° angle. Other angles are possible by varying the bevel on the gears. Common examples include a hand driven kitchen beater, and the differential in a car.

Worm gears:

Worm gears are also valuable in transmitting torque from one shaft to another at a 90° angle. They also reduce the speed of the rotating gear wheel. A worm gear train consists of a standard gear wheel on a drive shaft, with an endless screw that meshes with the gear wheel as it is turned. This type of gear is useful for fine adjustments, as a large number of rotations of the "worm" results in many fewer rotations of the gear. Its uses include fine tuning of radio receivers where precision is important.

Rack and Pinion gears

This form of gearing is used to transmit rotational motion of a gear wheel to a straight bar with teeth. The rack and pinion was once common in car steering systems. There are stops at the end of the straight section to limit movement.

A rack and pinion is a type of linear actuator that comprises a circular gear (the pinion) engaging a linear gear (the rack), which operate to translate rotational motion into linear motion. Driving the pinion into rotation causes the rack to be driven linearly

Internal gear

Internal gear is a gear with its teeth cut in the internal surface of a cylinder and meshes with spur gears.

Internal gears are often used in applications involving planetary gear drives and gear couplings. There are three major types of planetary gear mechanisms: planetary, solar and star types. Depending on the type and the pattern of which shafts act as input and output, many variations of speed transmission ratios and rotational directions are produced.

An internal gear is a round wheel with grooves on the inside of the wheel that allow

A quick review:

Simple machines are non-motorized devices that change the direction or magnitude of a force. 6 basic types are: lever, pulley, wheel and axle, inclined plane, screw, and wedge. Compound machines. More than one simple machine connected to each other. Efficiency: The comparison of IMA to AMA. How good is the simple machine at doing its job? IMA= Ideal Mechanical Advantage. In a perfect system with no friction or loss of energy, your ratio of output to input force. AMA= Actual Mechanical Advantage. Actual output force/actual input force. Takes into account factors influencing actual work done, such as friction, flex, wear. Coefficient of Friction. the ratio of the force of friction between two bodies and the force pressing them together. Essentially, how well things stick to each other due to friction:

Compound machines:

Compound machines are just machines that are made up of two or more simple machines. Simple machines include a wedge, an inclined plane (like a ramp), a screw, a pulley, a wheel and axle, and a lever.

SOME EXAMPLES OF COMPOUND MACHINES:

Three common examples of compound machines are a shovel, a wheelbarrow, and a bicycle. These things make hard work easier.

A machine consisting of two or more simple machines operating together, as a wheelbarrow consisting of a lever, axle, and wheel.

The SI unit of work (and energy) is the joule (J), which is equal to the energy required to apply one newton of force applied over a distance of one meter

(J=N⋅m).

Work can be negative. For example, if object 2 is transferring mechanical energy to object 1, then the work done by object 1 is negative. Emphasis should be put on the difference between work done on and work done by. The work done on an object refers to the mechanical energy transferred to that object, whereas work done by an object refers to the mechanical energy transferred from that object to another.

The amount of work performed by a force can be represented by the formula

W=F⋅d

W=F⋅d, in which "W" represents the work applied, "F" represents the amount of force, and "d" represents the distance over which the force is applied.

If the angle formed by the force and the displacement is

θ

θ, then the work that

F

F does on the object is given by

Work

Work is the product of force and displacement. In physics, a force is said to do work if, when acting, there is a movement of the point of application in the direction of the force.

Force:

In physics, a force is any interaction that, when unopposed, will change the motion of an object. A force can cause an object with mass to change its velocity, i.e., to accelerate. Force can also be described intuitively as a push or a pull. A force has both magnitude and direction, making it a vector quantity.

You can apply force to an object without work. Say you car is stuck in the snow. You shovel and shovel for hours but you never make a diffrence. You try to get in the car and drive but you are still stuck. You applied force but you did not apply work.

More work

When you pull a sled through the snow you are exhibiting force and causing motion.

WORK=FORCE x DISTANCE

THIS IS THE WORK PYRAMID

WORK

FORCE / DISTANCE

Measuring force

Forces can be measured using a device called force meter. The unit of force is called the Newton. It is represented by the symbol N. A force of 2N is smaller than 7N.

Forces can be measured using a device called force meter. The unit of force is called the Newton. It is represented by the symbol N. A force of 2N is smaller than 7N.