Question

Scott needs to split a chunk of wood for the fire. There is a crack in the chunk. If he uses an axe it will use 200 Joules of energy. He receives 100 Joules of work out of the machine.
A) What type of simple machine has he used?
B) What is the efficiency of the machine?

Answer 1

Answer:

A) A wedge

B) The efficiency of the machine is 50%

Explanation:

The type of simple machine Scott used is the wedge

A) A wedge is a simple machine that consists of a long thick metal or wood stem that tapers to a thin (Relatively sharp) end. It is used for a splitting, tightening,  and lifting.

An example of a wedge is an axe

B) The efficiency of a machine is given approximately as the ratio of the work output to the work input as follows;

The amount of input energy the axe uses = 200 Joules

The amount of output work Scott receives from the axe  = 100 Joules

Therefore, the efficiency of the machine, η, is given as follows;

$\eta = \dfrac{The \ out.put \ work \ Scott \ receives \ from \ the \ axe}{The \ amount \ of \ in.put \ energy \ the \ axe \ uses} \times 100$

$\therefore \eta = = \dfrac{100 \ J}{200 \ J} \times 100 = 50\%$

The efficiency of the machine, η = 50%