Suppose you spend 30.0 minutes on a stair-climbing machine, climbing at a rate of 85 steps per minute, with each step 8.00 inches high. If you weigh 150 lb and the machine reports that 690 kcal have been burned at the end of the workout, what efficiency is the machine using in obtaining this result?

The efficiency of the machine  is  12%

Explanation:

From the question we are told that

    The time available to climb the stairs is  

    The rate at which the stairs is  climbed is  

     The height of each step is  

      The mass of the person is  

      The amount of calories burned is  

Generally the workdone is taking a step is mathematically represented as

Here  g (acceleration due to gravity is  )

substituting values

Now the total workdone during the course of the workout is mathematically represented as

substituting values

 The efficiency of the machine is mathematically represented as

substituting values  

            12%

what experimental evidence led scientists to change from the previous model to this one?

a few of the positive particles aimed at a gold foil seemed to bounce back.

the colors of light emitted from heated atoms had very specific energies.

experiments with water vapor showed that elements combine in specific proportions.

cathode rays were bent in the same way whenever a magnet was brought near them.

that the claims meet official rules.

don't misinterpret the claims