# Feedback Q&A on Machines

by Ron Kurtus

Readers have sent in a total of 14 comments and questions on Machine issues. They are listed according to date.

## List of most recent 10 letters

### Country

Lever is Simple Machine Ratio of lengths in a lever Uganda

Lever is Simple Machine What are the machines that use levers? RSA

Mechanical Advantage Gears on a bicycle Kenya

Machines What is the formula to find the work wasted? Philippines

Machines Is it possible to make 100% efficient engine? India

Lever is Simple Machine Uses of levers USA

Lever is Simple Machine Relationship between lever and force Malaysia

Machines How does performance vary with frequency? India

Machines What kind of motion is in a sewing machine? Nepal

Lever is Simple Machine Why doesn't the lever break at the point of contact? India

Next 10

## Ratio of lengths in a lever

Topic: Lever is Simple Machine

### Question

August 12, 2012

By means of a lever,a load of 200N is raised through a distance of 3m by a force of 75N.If the effort moves through 15m.

TINDEKA - Uganda

22836

You can find the ratio of the arm lengths of the lever by the ratio of the force and load. 200/75 = 8/3, where the short arm is closest to the load. Thus, to raise the load 3m, the effort must move 8m.

If the effort moves 15m, the load would move 15*3/8 meters.

## What are the machines that use levers?

Topic: Lever is Simple Machine

### Question

July 19, 2012

My question is that ,what are the machines that use levers?

bongiwe - RSA

22792

Any machine that has a handle that you turn uses a lever. A crane that lifts objects uses the lever principle. A wheel barrel is a form of lever. A shovel is a lever. There are many examples, if you look around you.

## Gears on a bicycle

### Question

June 1, 2012

The driving wheel of a bicycle of radius 10cm has 24 teeth. The driven wheel is of radius 4cm with 8 teeth.
What is the effect of increasing;
1)the number of teeth on the driving wheel.
2)the radius of the driven wheel.
3)why is it unrealistic to have both wheels with the same radius and an equal number of teeth?

Martin - Kenya

22694

It is assumed that there is a chain between the gears, or do they interact directly?

The separation of the teeth for the two wheels should be the same, otherwise the wheels do not work properly. With your numbers, the separation is not the same.

Increasing the radius of the driven wheel means that it will turn slower but with more power.

If you have both wheels or gears the same size and with the same number of teeth, there is not mechanical advantage. However, it does have the advantage of driving the rear bicycle wheel while peddling the driving gear placed in the middle of the bicycle.

## What is the formula to find the work wasted?

Topic: Machines

### Question

November 23, 2011

What is the formula to find the work wasted? Thank You .. I just need it for today!

Shaina - Philippines

22199

Work that is wasted or lost in a machine can be due to friction, heat or various inefficiencies. Unfortunately, there is no single formula to calculate the loss. It can be measured experimentally by comparing the expended energy with the output energy or work.

## Is it possible to make 100% efficient engine?

Topic: Machines

### Question

November 10, 2011

Is it possible to make 100% efficient engine?

krishna - India

22161

Unfortunately, there are losses due to friction and heat that reduce the efficiency of a machine to be less than 100%. Also, some processes in creating energy are much less that 100%.

## Uses of levers

Topic: Lever is Simple Machine

### Question

March 26, 2011

WHAT ARE THE USE OF LEVERS

MISTURA - USA

21388

You can use a lever to lift a heavy object. Levers can be used to hold items, such as with pliers.

## Relationship between lever and force

Topic: Lever is Simple Machine

### Question

September 19, 2010

What is the relationship between the length of level with the force? Let say the length of the level increse, does this means the force needed will decrease?

Thanks.

Zulfariz - Malaysia

20408

It is both the length of the lever and the location of the pivot point that determine how much force you must apply to lift a weight. If the side where you apply to force these further from the pivot point man on the side with the weight, you can lift a heavier weight.

## How does performance vary with frequency?

Topic: Machines

### Question

August 16, 2010

how the performance of machine varies with frequency

arjunan - India

20243

It depends on the type of machine. If it is an engine, there is a peak frequency for performance. If it is an electrical device, it is usually set to perform best at the applied frequency.

## What kind of motion is in a sewing machine?

Topic: Machines

### Question

June 4, 2010

What kind of motion (linear or oscillatory) is shown by sewing machine?

Ramesh - Nepal

19839

A sewing machine usually has a wheel and shaft that are in rotating motion. The shaft turns a crank that moves the needle up and down in oscillating motion. The movement of the cloth under the needle is usually linear or straight line motion.

## Why doesn't the lever break at the point of contact?

Topic: Lever is Simple Machine

### Question

May 13, 2010

why the lever don't break at the point of contact of fulcrum and lever when we apply the force to move the load ?

dinesh - India

19715

In some cases, when the lever is made out of weak materials, it can break at the point of contact. You need to make sure that the lever is strong enough to lift your load without bending or breaking.

Next 10

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