30 Questions
Which type of lever has the effort between the load and the fulcrum?
Third class lever
When using an inclined plane, why does the user have to move a greater distance than the load?
To increase mechanical advantage
What type of force does a wedge allow the user to apply on an object?
Shear force
In which type of lever is the fulcrum positioned between the load and the point of effort?
First class lever
Why must a wedge be used in only one direction?
To push objects apart
How does the mechanical advantage change when using a second-class lever compared to a third-class lever?
Increases in a second-class lever
What is the mechanical advantage of each pulley segment in the block and tackle system?
1
In the wheel and axle machine, which part is considered the 'wheel'?
The part that is larger in diameter
What type of motion does force create in a wheel and axle machine?
Angular motion
In the context of complex machine development, what happened as larger communities developed?
More complicated machines developed
What term is used to describe force that follows a circular motion in a wheel and axle machine?
Torque force
How many times does the larger wheel of a wheel and axle machine turn during one revolution?
Once
What factor is affected by friction when considering the mechanical advantage of a device?
Mechanical advantage
What causes friction between materials?
Roughness of materials
How does friction affect the efficiency of an appliance?
Decreases efficiency
In the context of work, when is work considered to be done?
When a force is applied on an object
Amy uses 20N of force to push a lawn mower 10 meters. What is the work done by Amy?
$200$ Joules
What does the work input represent in the context of using an inclined plane to lift a person in a wheelchair?
$320$N for 5 meters
What is the formula for calculating work given a force and distance?
$W = F \times d$
If Amy exerts 20N of force to push a lawn mower 10 meters, how much work does she do?
200 Joules
Why does the same amount of work get done regardless of mechanical advantage in using a machine?
Less force is required when using a machine
In a hydraulic system, what is pressure?
A measure of the force applied to a given area
Why does friction cause the work input to not equal the work output in real situations?
Friction dissipates energy
What is the impact of an inclined plane on the force needed to lift an object vertically?
Decreases the force required
What negatively affects the efficiency of a system according to the text?
Energy loss due to friction
In a real-world pulley system, what contributes to energy loss?
Friction
Where does most of the energy go in a very inefficient complex machine?
Heat generation
What is the efficiency of an appliance that supplies 8100J of useful energy when the total input energy is 9000J?
90%
If an appliance has an efficiency of 25% and is supplied with 9000J, what is its useful output energy?
2250J
When a system has an efficiency of 90% and is supplied with 9000J, what is its useful output energy?
7200J
Study Notes
Types of Levers
- A lever is a rigid bar or plank that can rotate around a fixed point called a pivot or fulcrum.
- There are three types of levers:
- First class lever: fulcrum between the load and the point of effort.
- Second class lever: load is between the effort and the fulcrum.
- Third class lever: effort is between the load and the fulcrum.
Inclined Planes
- An inclined plane is a flat surface at an angle to another flat surface, such as the ground.
- Enables the user to move a larger load than without, but the user must move a greater distance than the load.
- The ramp cannot be too steep in order to work.
Wedges
- A wedge is similar to an inclined plane, but is forced into an object.
- By pressing on the wide end, the narrow end splits the object.
- Can only be used in one direction, to push objects apart.
- Enables the user to apply a greater force on an object, but the user must move a greater distance than the split.
Efficiency and Work
- Work is done when a force acts on an object to make the object move.
- Efficiency is the measurement of how well a machine or device uses energy.
- Efficiency is negatively affected by friction, which causes energy loss and converts it into heat.
Wheel and Axle
- A wheel and axle is a machine made up of two wheels of different diameters that turn together.
- The larger wheel is considered the ‘wheel’ while the smaller wheel is considered the ‘axle’.
- Force is usually linear, but when it follows a circular motion, it is called torque.
Complex Machines
- A complex machine is a combination of simple machines.
- Complex machines are often inefficient due to energy loss caused by friction.
- Most complex machines waste energy, and only a small percentage is useful output energy.
Friction
- Friction is a force that opposes motion.
- Friction can be an important factor in a mechanical system because it opposes motion.
- Friction affects a machine’s efficiency, and most energy is lost and unusable (e.g., lost as heat).
Learn about the different types of levers - first class, second class, and third class - and how they function. Understand the positioning of the fulcrum, load, and effort in each type of lever.
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