FORM 2-PHYSICS-TOPIC 5-SIMPLE MACHINES
A simple machine is a non-powered mechanical device that changes the direction or magnitude of a force. In general, they can be defined as the simplest mechanisms that use mechanical advantage (also called leverage) to multiply force. A simple machine uses a single applied force to do work against a single load force. Ignoring friction losses, the work done on the load is equal to the work done by the applied force.
The Structure of a Wheel and Axle
Describe the structure of a wheel and axle
Structure of Wheel and Axle
A wheel and axle is a simple machine that consists of a wheel and axle mounted with the same axis of rotation. The radius of the wheel is always greater than that of the axle.
Consider the diagram below:
Wheel and Axle
The Mechanical Advantage, Velocity Ratio and Efficiency of a Wheel and Axle
Determine the mechanical advantage, velocity ratio and efficiency of a wheel and axle
Mechanical advantage of Wheel and Axle
M.A = Load/Effort
Velocity ratio ( V.R)= radius of wheel (R)/radius of axle (r)
Example 8
Example 1
A wheel and axle of efficiency 80% is used to raise a load of 2000N. If the radius of the wheel is 50cm, and that of the axle is 2cm, calculate
- The velocity ratio and mechanical Advantage of machine
- The effort required to overcome the load
Solution
Data given
Efficiency = 80%
Load = 2000N
Radius of wheel (R)= 50cm
Radius of axle (r) = 2cm
V.R=?
M.A=?
Effort?
-
The Wheel and Axle in Daily Life
Use the wheel and axle in daily life
Application of Wheel and Axle
Wheels help people do work in two ways. First, likeleversorinclined planes, wheels allow you to do something easy for a longer time, instead of doing something hard for a shorter time. If you turn a large wheel fixed to an axle, the axle will also turn. You can turn the large wheel easily (but it takes a lot of turning to go all the way around).
The axle will go around a much shorter distance, but with more force. So you can use a wheel to create a mechanical advantage - you can turn something heavy, by spinning a large wheel attached to an axle that is attached to the heavy thing.
That's how a pencil sharpener works. Or, you can do it the other way around - use a lot of force to turn the axle, and that will spin the wheels really fast. That's what cars do.Wheels are the most important part of pottery wheels, wagons and cars, but also ofwheelbarrows,spinning wheels, water wheels, windmills, andpulleys.
Also, wheels on a wagon only touch the ground at one spot at a time, keeping the rest of the wagon off the ground. This makes lessfriction, so that the wagon is easier to move than if you were pulling it along like a sled.
