Question

 

Part A: Define actual and theoretical mechanical advantage, using words as well as equations.

Part B: What law of physics forbids the efficiency of an actual machine from being equal to 1? (100% efficiency)

Part C: What is the efficiency of a wooden ramp (μ =0.2) at an angle of 39 degrees?

Part D: Is a screw an example of a wheel and axle, lever, or inclined plane?

Answer 1

PART A: A mechanical advantage where it is assumed that there is no friction, no wear and tear, etc can be called as theoretical mechanical advantage. It usually conveys the the maximum overall efficiency of a machine. Another assumption is that the force input of machine is equal to force output of the machine. In short there aare no losses. It is also assumed that, Input power is equal to output power. thus, the power is constant through out the machine. This can be understood by the below equation as well,

Where f is force.

A mechanical advantage which is calculated using the values of input and output forces is called Actual mechanical advantage. It considers friction, wear and other losses into calculation. Actual mechanical advantage can be caalulated as the ratio of the experimentally derived output force to the experimentally derived Input force.

where f is experimentally derived.

PART B: first law of thermodynamcis forbids the efficiency of an actual machine from being eual to 1. The first law states that Energy can neither be created nor be destroyed, it can only be converted from one form to another. so, the input energy is converted into various forms of energies other than required output form of energy due to friction, wear, etc. Thus, efficeincy cant be 1.

PART D: Screw is a form of Twisted inclined plane. So, Screw is not an example of any of the simple machines mentioned in the question, It is a twisted form of inclined plane or it is in itself one of the basic simple machine.