Answer:
Work done, W = 1.44 kJ
Explanation:
Given that,
Mass of boy, m = 74 kg
Initial speed of boy, u = 1.6 m/s
The boy then drops through a height of 1.56 m
Final speed of boy, v = 8.5 m/s
To find,
Non-conservative work was done on the boy.
Solution,
The work done by the non conservative forces is equal to the sum of total change in kinetic energy and total change in potential energy.



W = 1447.21 Joules
or
W = 1.44 kJ
Therefore, the non conservative work done on the boy is 1.44 kJ.
Answer:
so what ever one is new here
Answer:
the ratio of the kinetic energy of an electron to that of a proton if their wavelengths are equal is 1835.16 .
Explanation:
We know, wavelength is expressed in terms of Kinetic Energy by :

Therefore , 
It is given that both electron and proton have same wavelength.
Therefore,
.... equation 1.
.... equation 2.
Now, dividing equation 1 by 2 .
We get ,

Putting value of mass of electron =
and mass of proton = 
We get :

Hence , this is the required solution.
8.33 m/s
Explain:
If you understand what 1 km = 1000 m and 1 hr = 60*60 seconds signify, you already know what they mean. If you translate 1000 m/ 3600 s to km/hr, you'll get 5 m/ 18 s, which you can multiply by 30 to get (30 x 5)/18 = 8.33 m/s.