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.

83.34%.

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 :

So, the efficiency of the machine is 83.34%.

1 the 4 is sig

when a device is used in a circuit in which the voltage is 81 v, the current flowing through the device is 3 a. what is the resistance of the device?

a. 27 ω

b. 40.5 a

c. 243 ω

d. 243 a

the correct answer is a. 27