Question

Lucy needs to lift a crate to a shelf 20 m high. She does 12,000 J of work on a machine to help her. The machine exerts a force of 500 N to lift the crate.

Answer 1

83%

Step-by-step explanation:

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Answer 2

83.34%.

Step-by-step explanation:

Given that,

Lucy does 12,000 J of work on a machine to help her

The machine exerts a force of 500 N to lift the crate.

Height of the shelf = 20 m

We need to find the efficiency of the machine. The ratio of output work to the input work is called the efficiency of any machine. It is given by :

`\eta=(W_o)/(W_i)* 100\\\\=(500* 20)/(12000)\\\\=83.34\%`

So, the efficiency of the machine is 83.34%.