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%

adding a(n) to an electric circuit would increase the magnetic field around a wire;

b. solenoid

a solenoid is a type of electromagnet whose purpose is to generate a controlled magnetic field.

if the purpose of the solenoid is instead to impede changes in the electric current, a solenoid can be more specifically classified as an inductor rather than an electromagnet.

the minimum constant speed at which she can catch the train is 2.7 m/s

given:

acceleration = 0.6

time = 4.5 s

to find:

velocity = ?

formula used:

from 1st kinematic equation we get,

v = u + at

u = initial speed of train = 0 m/s

v = final speed of the train

a = acceleration of the train

t = time

solution:

from 1st kinematic equation we get,

v = u + at

u = initial speed of train = 0 m/s

v = final speed of the train

a = acceleration of the train

t = time

v = 0 + (0.6 × 4.5)

v = 2.7 m/s

the minimum constant speed at which she can catch the train is 2.7 m/s