Chemical change is any change that results in the formation of new chemical substances. At the molecular level, chemical change involves making or breaking of bonds between atoms. These changes are chemical: iron rusting (iron oxide forms) gasoline burning (water vapor and carbon dioxide form)
The theorist you are talking about is none other than Abraham Maslow. He developed the Maslow's hierarchy of needs wherein basic human needs range from the physiological, security, and love and belongingness needs to the esteem and self-actualization of the individual.
Answer:
VR = 
Explanation:
A machine is a device that can be used to overcome a load by the application of an effort through a pivot. Examples are: pulleys, wedge, screw jack, wheel and axle etc.
The wheel and axle is a simple device that can be used to lift a load through a height. Its velocity ratio (VR) can be determined by:
VR = 
Note that for a practical wheel and axle, the radius of the wheel is greater than the radius of the axle.